feat: Return location info and Hijri date from the prayer times endpoint

internal/api/api.go

@@ -16,6 +16,7 @@ import (
 	"github.com/gofiber/fiber/v3/middleware/recover"
 	"github.com/gofiber/fiber/v3/middleware/static"
 
+	"prayertimes/pkg/hijricalendar"
 	"prayertimes/pkg/prayer"
 	"prayertimes/templates"
 )
@@ -30,8 +31,8 @@ type Services struct {
 }
 
 type PrayerProvider interface {
-	Get(ctx context.Context, locationID string) ([]prayer.Times, error)
-	GetByCoords(ctx context.Context, coords prayer.Coordinates) ([]prayer.Times, error)
+	Get(ctx context.Context, locationID string) (prayer.TimesResult, error)
+	GetByCoords(ctx context.Context, coords prayer.Coordinates) (prayer.TimesResult, error)
 }
 
 type LocationProvider interface {
@@ -71,6 +72,7 @@ func New(services Services) *fiber.App {
 			LocationID string `query:"location_id"`
 			Latitude   string `query:"latitude"`
 			Longitude  string `query:"longitude"`
+			UTC        string `query:"utc"`
 		}
 		if err := ctx.Bind().Query(&query); err != nil {
 			return fmt.Errorf("failed to bind prayer times query parameters: %w", errors.Join(fiber.ErrBadRequest, err))
@@ -79,15 +81,16 @@ func New(services Services) *fiber.App {
 		locationID := strings.TrimSpace(query.LocationID)
 		latitude := strings.TrimSpace(query.Latitude)
 		longitude := strings.TrimSpace(query.Longitude)
+		utc := strings.TrimSpace(query.UTC) == "1"
 
 		var (
-			times []prayer.Times
-			err   error
+			result prayer.TimesResult
+			err    error
 		)
 
 		switch {
 		case locationID != "":
-			times, err = services.PrayerProvider.Get(ctx.Context(), locationID)
+			result, err = services.PrayerProvider.Get(ctx.Context(), locationID)
 		case latitude != "" && longitude != "":
 			lat, latErr := strconv.ParseFloat(latitude, 64)
 			if latErr != nil {
@@ -98,7 +101,7 @@ func New(services Services) *fiber.App {
 				return fmt.Errorf("failed to parse longitude query parameter: %w", errors.Join(fiber.ErrBadRequest, lngErr))
 			}
 
-			times, err = services.PrayerProvider.GetByCoords(ctx.Context(), prayer.Coordinates{
+			result, err = services.PrayerProvider.GetByCoords(ctx.Context(), prayer.Coordinates{
 				Latitude:  lat,
 				Longitude: lng,
 			})
@@ -110,9 +113,33 @@ func New(services Services) *fiber.App {
 			return fmt.Errorf("failed to fetch prayer times: %w", err)
 		}
 
+		location := result.Location
+		if location.Latitude != 0 || location.Longitude != 0 {
+			locations, locErr := services.LocationProvider.SearchLocationsByCoords(ctx.Context(), prayer.Coordinates{
+				Latitude:  location.Latitude,
+				Longitude: location.Longitude,
+			})
+			if locErr != nil {
+				return fmt.Errorf("failed to enrich prayer times location from database: %w", locErr)
+			}
+			if len(locations) > 0 {
+				dbLocation := locations[0]
+				if strings.TrimSpace(dbLocation.Timezone) == "" {
+					dbLocation.Timezone = location.Timezone
+				}
+				location = dbLocation
+			}
+		}
+
+		mappedTimes, err := mapPrayerTimesForResponse(result.Times, location, utc)
+		if err != nil {
+			return fmt.Errorf("failed to map prayer times for response: %w", err)
+		}
+
 		ctx.Response().Header.Set(fiber.HeaderCacheControl, "max-age=86400")
 		return ctx.JSON(fiber.Map{
-			"prayertimes": times,
+			"location":    location,
+			"prayertimes": mappedTimes,
 		})
 	})
 
@@ -169,3 +196,100 @@ func New(services Services) *fiber.App {
 
 	return app
 }
+
+type prayerTimesResponse struct {
+	Date      string `json:"date"`
+	DateHijri string `json:"date_hijri"`
+	Fajr      string `json:"fajr"`
+	Sunrise   string `json:"sunrise"`
+	Dhuhr     string `json:"dhuhr"`
+	Asr       string `json:"asr"`
+	Sunset    string `json:"sunset,omitempty"`
+	Maghrib   string `json:"maghrib"`
+	Isha      string `json:"isha"`
+}
+
+func mapPrayerTimesForResponse(times []prayer.Times, location prayer.Location, utc bool) ([]any, error) {
+	if utc {
+		result := make([]any, 0, len(times))
+		for _, item := range times {
+			dateHijri := item.DateHijri
+			if dateHijri == "" {
+				dateHijri = hijricalendar.ToISODate(item.Date)
+			}
+
+			result = append(result, prayer.Times{
+				Date:      item.Date.UTC(),
+				DateHijri: dateHijri,
+				Fajr:      item.Fajr.UTC(),
+				Sunrise:   item.Sunrise.UTC(),
+				Dhuhr:     item.Dhuhr.UTC(),
+				Asr:       item.Asr.UTC(),
+				Sunset:    item.Sunset.UTC(),
+				Maghrib:   item.Maghrib.UTC(),
+				Isha:      item.Isha.UTC(),
+			})
+		}
+		return result, nil
+	}
+
+	tz := time.UTC
+	if strings.TrimSpace(location.Timezone) != "" {
+		loadedTZ, err := loadTimezone(location.Timezone)
+		if err != nil {
+			return nil, fmt.Errorf("failed to load location timezone: %w", err)
+		}
+		tz = loadedTZ
+	}
+
+	result := make([]any, 0, len(times))
+	for _, item := range times {
+		dateHijri := item.DateHijri
+		if dateHijri == "" {
+			dateHijri = hijricalendar.ToISODate(item.Date)
+		}
+
+		result = append(result, prayerTimesResponse{
+			Date:      item.Date.In(tz).Format(time.DateOnly),
+			DateHijri: dateHijri,
+			Fajr:      formatHHMM(item.Fajr, tz),
+			Sunrise:   formatHHMM(item.Sunrise, tz),
+			Dhuhr:     formatHHMM(item.Dhuhr, tz),
+			Asr:       formatHHMM(item.Asr, tz),
+			Sunset:    formatHHMM(item.Sunset, tz),
+			Maghrib:   formatHHMM(item.Maghrib, tz),
+			Isha:      formatHHMM(item.Isha, tz),
+		})
+	}
+
+	return result, nil
+}
+
+func formatHHMM(value time.Time, tz *time.Location) string {
+	if value.IsZero() {
+		return ""
+	}
+	return value.In(tz).Format("15:04")
+}
+
+func loadTimezone(name string) (*time.Location, error) {
+	if strings.HasPrefix(name, "UTC") {
+		offsetText := strings.TrimPrefix(name, "UTC")
+		if offsetText == "" {
+			return time.UTC, nil
+		}
+
+		offsetHours, err := strconv.Atoi(offsetText)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse utc offset timezone: %w", err)
+		}
+		return time.FixedZone(name, offsetHours*3600), nil
+	}
+
+	loc, err := time.LoadLocation(name)
+	if err != nil {
+		return nil, fmt.Errorf("failed to load iana timezone: %w", err)
+	}
+
+	return loc, nil
+}

pkg/citydb/provider.go

@@ -48,6 +48,7 @@ type locationRow struct {
 	ASCIIName      string  `db:"ascii_name"`
 	AlternateNames string  `db:"alternate_names"`
 	CountryCode    string  `db:"country_code"`
+	Timezone       string  `db:"timezone"`
 	Latitude       float64 `db:"latitude"`
 	Longitude      float64 `db:"longitude"`
 	DistanceSq     float64 `db:"distance_sq"`
@@ -69,6 +70,7 @@ func (p Provider) SearchLocations(ctx context.Context, query string) ([]prayer.L
 			goqu.I("ascii_name"),
 			goqu.COALESCE(goqu.I("alternate_names"), "").As("alternate_names"),
 			goqu.I("country_code"),
+			goqu.I("timezone"),
 			goqu.I("latitude"),
 			goqu.I("longitude"),
 			goqu.V(0).As("distance_sq"),
@@ -96,6 +98,7 @@ func (p Provider) SearchLocations(ctx context.Context, query string) ([]prayer.L
 			ASCIIName:      row.ASCIIName,
 			AlternateNames: row.AlternateNames,
 			CountryCode:    row.CountryCode,
+			Timezone:       row.Timezone,
 			Latitude:       row.Latitude,
 			Longitude:      row.Longitude,
 		})
@@ -113,6 +116,7 @@ func (p Provider) SearchLocationsByCoords(ctx context.Context, coords prayer.Coo
 			goqu.I("ascii_name"),
 			goqu.COALESCE(goqu.I("alternate_names"), "").As("alternate_names"),
 			goqu.I("country_code"),
+			goqu.I("timezone"),
 			goqu.I("latitude"),
 			goqu.I("longitude"),
 			goqu.L(
@@ -142,6 +146,7 @@ func (p Provider) SearchLocationsByCoords(ctx context.Context, coords prayer.Coo
 			ASCIIName:      row.ASCIIName,
 			AlternateNames: row.AlternateNames,
 			CountryCode:    row.CountryCode,
+			Timezone:       row.Timezone,
 			Latitude:       row.Latitude,
 			Longitude:      row.Longitude,
 		})

pkg/diyanetapi/provider.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/imroc/req/v3"
 
+	"prayertimes/pkg/hijricalendar"
 	"prayertimes/pkg/prayer"
 )
 
@@ -21,18 +22,20 @@ func New(c *req.Client) Provider {
 	}
 }
 
-func (d Provider) GetByCoords(ctx context.Context, coords prayer.Coordinates) ([]prayer.Times, error) {
+func (d Provider) GetByCoords(ctx context.Context, coords prayer.Coordinates) (prayer.TimesResult, error) {
 	locationID, err := d.getLocationIDByCoords(ctx, coords)
 	if err != nil {
-		return nil, fmt.Errorf("failed to resolve location by coordinates: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to resolve location by coordinates: %w", err)
 	}
 
-	times, err := d.Get(ctx, locationID)
+	result, err := d.Get(ctx, locationID)
 	if err != nil {
-		return nil, fmt.Errorf("failed to get prayer times by coordinates: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to get prayer times by coordinates: %w", err)
 	}
+	result.Location.Latitude = coords.Latitude
+	result.Location.Longitude = coords.Longitude
 
-	return times, nil
+	return result, nil
 }
 
 func (d Provider) getLocationIDByCoords(ctx context.Context, coords prayer.Coordinates) (string, error) {
@@ -66,27 +69,32 @@ func (d Provider) getLocationIDByCoords(ctx context.Context, coords prayer.Coord
 	return fmt.Sprintf("%d", response.ResultObject[0].ID), nil
 }
 
-func (d Provider) Get(ctx context.Context, locationID string) ([]prayer.Times, error) {
+func (d Provider) Get(ctx context.Context, locationID string) (prayer.TimesResult, error) {
 	res, err := d.http.NewRequest().
 		SetContext(ctx).
 		SetQueryParam("ilceId", locationID).
 		Get("https://namazvakti.diyanet.gov.tr/api/NamazVakti/Gunluk")
 	if err != nil {
-		return nil, fmt.Errorf("failed to get prayer times by location id: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to get prayer times by location id: %w", err)
 	}
 
-	times, err := d.parseResponse(res)
+	result, err := d.parseResponse(res)
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse prayer times response: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to parse prayer times response: %w", err)
 	}
+	result.Location.ID = parseIntOrZero(locationID)
 
-	return times, nil
+	return result, nil
 }
 
-func (d Provider) parseResponse(res *req.Response) ([]prayer.Times, error) {
+func (d Provider) parseResponse(res *req.Response) (prayer.TimesResult, error) {
 	var response struct {
 		Success      bool `json:"success"`
 		ResultObject struct {
+			Location struct {
+				ID       int    `json:"konum_Id"`
+				Timezone string `json:"timezone"`
+			} `json:"konum"`
 			PrayerTimes []struct {
 				Date        time.Time `json:"miladi_tarih_uzun_Iso8601"`
 				DateIslamic string    `json:"hicri_tarih_uzun"`
@@ -101,14 +109,14 @@ func (d Provider) parseResponse(res *req.Response) ([]prayer.Times, error) {
 		} `json:"resultObject"`
 	}
 	if err := res.Unmarshal(&response); err != nil {
-		return nil, fmt.Errorf("failed to unmarshal as json: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to unmarshal as json: %w", err)
 	}
 	if !response.Success {
-		return nil, fmt.Errorf("failed to get prayer times from upstream: %w", errors.New(res.String()))
+		return prayer.TimesResult{}, fmt.Errorf("failed to get prayer times from upstream: %w", errors.New(res.String()))
 	}
 
 	if len(response.ResultObject.PrayerTimes) == 0 {
-		return nil, nil
+		return prayer.TimesResult{}, nil
 	}
 
 	var times []prayer.Times
@@ -120,16 +128,29 @@ func (d Provider) parseResponse(res *req.Response) ([]prayer.Times, error) {
 		}
 
 		times = append(times, prayer.Times{
-			Date:        pt.Date.Format(time.DateOnly),
-			DateIslamic: pt.DateIslamic,
-			Fajr:        pt.Fajr.Format("15:04"),
-			Sunrise:     pt.Sunrise.Format("15:04"),
-			Dhuhr:       pt.Dhuhr.Format("15:04"),
-			Asr:         pt.Asr.Format("15:04"),
-			Sunset:      pt.Sunset.Format("15:04"),
-			Maghrib:     pt.Maghrib.Format("15:04"),
-			Isha:        pt.Isha.Format("15:04"),
+			Date:      pt.Date.UTC(),
+			DateHijri: hijricalendar.ToISODate(pt.Date.UTC()),
+			Fajr:      pt.Fajr.UTC(),
+			Sunrise:   pt.Sunrise.UTC(),
+			Dhuhr:     pt.Dhuhr.UTC(),
+			Asr:       pt.Asr.UTC(),
+			Sunset:    pt.Sunset.UTC(),
+			Maghrib:   pt.Maghrib.UTC(),
+			Isha:      pt.Isha.UTC(),
 		})
 	}
-	return times, nil
+
+	return prayer.TimesResult{
+		Location: prayer.Location{
+			ID:       response.ResultObject.Location.ID,
+			Timezone: response.ResultObject.Location.Timezone,
+		},
+		Times: times,
+	}, nil
+}
+
+func parseIntOrZero(value string) int {
+	var out int
+	_, _ = fmt.Sscanf(value, "%d", &out)
+	return out
 }

pkg/diyanetapi/provider_test.go

@@ -15,37 +15,37 @@ func TestDiyanetAPI_GetByCoords(t *testing.T) {
 	t.Run("by coords", func(t *testing.T) {
 		t.Parallel()
 
-		times, err := p.GetByCoords(context.Background(), prayer.Coordinates{
+		result, err := p.GetByCoords(context.Background(), prayer.Coordinates{
 			Latitude:  52.5100846,
 			Longitude: 13.4518284,
 		})
 		if err != nil {
 			t.Skipf("skipping live endpoint test due to upstream/network error: %v", err)
 		}
-		if len(times) == 0 {
+		if len(result.Times) == 0 {
 			t.Skip("skipping live endpoint test because upstream returned no times")
 		}
 
 		assert.NoError(t, err)
-		assert.NotEmpty(t, times)
-		t.Logf("%#+v", times[0])
+		assert.NotEmpty(t, result.Times)
+		t.Logf("location=%+v first=%+v", result.Location, result.Times[0])
 	})
 
 	t.Run("by id", func(t *testing.T) {
 		t.Parallel()
 
-		times, err := p.Get(context.Background(), "11104")
+		result, err := p.Get(context.Background(), "11104")
 		if err != nil {
 			t.Skipf("skipping live endpoint test due to upstream/network error: %v", err)
 		}
-		if len(times) == 0 {
+		if len(result.Times) == 0 {
 			t.Skip("skipping live endpoint test because upstream returned no times")
 		}
 
 		assert.NoError(t, err)
-		assert.NotEmpty(t, times)
-		for _, time := range times {
-			t.Log(time)
+		assert.NotEmpty(t, result.Times)
+		for _, item := range result.Times {
+			t.Log(item)
 		}
 	})
 }

pkg/diyanetcalc/provider.go

@@ -7,6 +7,7 @@ import (
 	"math"
 	"time"
 
+	"prayertimes/pkg/hijricalendar"
 	"prayertimes/pkg/prayer"
 )
 
@@ -84,11 +85,11 @@ func (Provider) SearchLocations(_ context.Context, _ string) ([]prayer.Location,
 	return nil, fmt.Errorf("failed to search locations: %w", errNotSupported)
 }
 
-func (Provider) Get(_ context.Context, _ string) ([]prayer.Times, error) {
-	return nil, fmt.Errorf("failed to get prayer times by location id: %w", errNotSupported)
+func (Provider) Get(_ context.Context, _ string) (prayer.TimesResult, error) {
+	return prayer.TimesResult{}, fmt.Errorf("failed to get prayer times by location id: %w", errNotSupported)
 }
 
-func (Provider) GetByCoords(_ context.Context, coords prayer.Coordinates) ([]prayer.Times, error) {
+func (Provider) GetByCoords(_ context.Context, coords prayer.Coordinates) (prayer.TimesResult, error) {
 	offset := estimateUTCOffsetHours(coords.Longitude)
 	todayUTC := time.Now().UTC().Truncate(24 * time.Hour)
 
@@ -98,18 +99,26 @@ func (Provider) GetByCoords(_ context.Context, coords prayer.Coordinates) ([]pra
 		calculated := prayerTimes(coords.Latitude, coords.Longitude, day)
 
 		results = append(results, prayer.Times{
-			Date:    day.Format(time.DateOnly),
-			Fajr:    formatHHMM(calculated.Imsak, offset),
-			Sunrise: formatHHMM(calculated.Sunrise, offset),
-			Dhuhr:   formatHHMM(calculated.Dhuhr, offset),
-			Asr:     formatHHMM(calculated.Asr, offset),
-			Sunset:  formatHHMM(calculated.Sunset, offset),
-			Maghrib: formatHHMM(calculated.Maghrib, offset),
-			Isha:    formatHHMM(calculated.Isha, offset),
+			Date:      day,
+			DateHijri: hijricalendar.ToISODate(day),
+			Fajr:      derefOrZero(calculated.Imsak),
+			Sunrise:   derefOrZero(calculated.Sunrise),
+			Dhuhr:     derefOrZero(calculated.Dhuhr),
+			Asr:       derefOrZero(calculated.Asr),
+			Sunset:    derefOrZero(calculated.Sunset),
+			Maghrib:   derefOrZero(calculated.Maghrib),
+			Isha:      derefOrZero(calculated.Isha),
 		})
 	}
 
-	return results, nil
+	return prayer.TimesResult{
+		Location: prayer.Location{
+			Latitude:  coords.Latitude,
+			Longitude: coords.Longitude,
+			Timezone:  formatUTCOffsetTimezone(offset),
+		},
+		Times: results,
+	}, nil
 }
 
 // Convert a calendar date to a Julian Day Number.
@@ -290,16 +299,15 @@ func prayerTimes(lat, lon float64, d time.Time) computedTimes {
 	}
 }
 
-// Convert UTC prayer time datetimes to HH:MM strings at a given UTC offset.
-//
-// tzOffset is UTC offset in hours, e.g. 3 for Turkey (UTC+3).
-func formatHHMM(dt *time.Time, tzOffset float64) string {
+func derefOrZero(dt *time.Time) time.Time {
 	if dt == nil {
-		return ""
+		return time.Time{}
 	}
+	return dt.UTC()
+}
 
-	tz := time.FixedZone("estimated", int(tzOffset*3600))
-	return dt.In(tz).Add(30 * time.Second).Format("15:04")
+func formatUTCOffsetTimezone(offset float64) string {
+	return fmt.Sprintf("UTC%+d", int(offset))
 }
 
 func estimateUTCOffsetHours(longitude float64) float64 {

pkg/diyanetprovider/provider.go

@@ -10,12 +10,12 @@ import (
 )
 
 type APIProvider interface {
-	Get(ctx context.Context, locationID string) ([]prayer.Times, error)
-	GetByCoords(ctx context.Context, coords prayer.Coordinates) ([]prayer.Times, error)
+	Get(ctx context.Context, locationID string) (prayer.TimesResult, error)
+	GetByCoords(ctx context.Context, coords prayer.Coordinates) (prayer.TimesResult, error)
 }
 
 type FallbackProvider interface {
-	GetByCoords(ctx context.Context, coords prayer.Coordinates) ([]prayer.Times, error)
+	GetByCoords(ctx context.Context, coords prayer.Coordinates) (prayer.TimesResult, error)
 }
 
 type Provider struct {
@@ -28,44 +28,44 @@ func New(api APIProvider, fallback FallbackProvider) Provider {
 	return Provider{
 		api:      api,
 		fallback: fallback,
-		timeout:  2 * time.Second,
+		timeout:  1 * time.Second,
 	}
 }
 
 var ErrEmptyTimes = errors.New("diyanet did not return any prayer times")
 
-func (p Provider) Get(ctx context.Context, locationID string) ([]prayer.Times, error) {
+func (p Provider) Get(ctx context.Context, locationID string) (prayer.TimesResult, error) {
 	ctxWithTimeout, cancel := context.WithTimeout(ctx, p.timeout)
 	defer cancel()
 
-	times, err := p.api.Get(ctxWithTimeout, locationID)
+	result, err := p.api.Get(ctxWithTimeout, locationID)
 	if err != nil {
-		return nil, fmt.Errorf("failed to get prayer times from api provider: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to get prayer times from api provider: %w", err)
 	}
-	if len(times) == 0 {
-		return nil, ErrEmptyTimes
+	if len(result.Times) == 0 {
+		return prayer.TimesResult{}, ErrEmptyTimes
 	}
 
-	return times, nil
+	return result, nil
 }
 
-func (p Provider) GetByCoords(ctx context.Context, coords prayer.Coordinates) ([]prayer.Times, error) {
+func (p Provider) GetByCoords(ctx context.Context, coords prayer.Coordinates) (prayer.TimesResult, error) {
 	ctxWithTimeout, cancel := context.WithTimeout(ctx, p.timeout)
 	defer cancel()
 
-	times, err := p.api.GetByCoords(ctxWithTimeout, coords)
-	if err == nil && len(times) > 0 {
-		return times, nil
+	result, err := p.api.GetByCoords(ctxWithTimeout, coords)
+	if err == nil && len(result.Times) > 0 {
+		return result, nil
 	}
 
-	times, err = p.fallback.GetByCoords(ctx, coords)
+	result, err = p.fallback.GetByCoords(ctx, coords)
 	if err != nil {
-		return nil, fmt.Errorf("failed to get prayer times from fallback provider: %w", err)
+		return prayer.TimesResult{}, fmt.Errorf("failed to get prayer times from fallback provider: %w", err)
 	}
 
-	if len(times) == 0 {
-		return nil, fmt.Errorf("fallback provider did not return any prayer times")
+	if len(result.Times) == 0 {
+		return prayer.TimesResult{}, fmt.Errorf("fallback provider did not return any prayer times")
 	}
 
-	return times, nil
+	return result, nil
 }

pkg/hijricalendar/calendar.go

@@ -0,0 +1,61 @@
+package hijricalendar
+
+import (
+	"fmt"
+	"math"
+	"time"
+)
+
+// JulianToIslamic converts a Julian calendar date to the Islamic (Hijri) calendar.
+// Algorithm from Jean Meeus, "Astronomical Algorithms", 2nd ed.
+func JulianToIslamic(year, month, day int) (iYear, iMonth, iDay int) {
+	jdn := julianToJDN(year, month, day)
+	return jdnToIslamic(jdn)
+}
+
+// GregorianToIslamic converts a Gregorian calendar date to the Islamic (Hijri)
+// calendar.
+func GregorianToIslamic(year, month, day int) (iYear, iMonth, iDay int) {
+	jdn := gregorianToJDN(year, month, day)
+	return jdnToIslamic(jdn)
+}
+
+// julianToJDN returns the Julian Day Number for a date on the Julian calendar.
+func julianToJDN(year, month, day int) int {
+	y, m := year, month
+	if m <= 2 {
+		y--
+		m += 12
+	}
+	return int(math.Floor(365.25*float64(y+4716))) +
+		int(math.Floor(30.6001*float64(m+1))) +
+		day - 1524
+}
+
+func gregorianToJDN(year, month, day int) int {
+	a := (14 - month) / 12
+	y := year + 4800 - a
+	m := month + 12*a - 3
+
+	return day + (153*m+2)/5 + 365*y + y/4 - y/100 + y/400 - 32045
+}
+
+// jdnToIslamic converts a Julian Day Number to an Islamic (Hijri) calendar date.
+// Source: F. de Moya, as cited in Meeus Ch. 9.
+func jdnToIslamic(jd int) (year, month, day int) {
+	l := jd - 1948440 + 10632
+	n := (l - 1) / 10631
+	l = l - 10631*n + 354
+	j := (10985-l)/5316*(50*l/17719) + (l/5670)*(43*l/15238)
+	l = l - (30-j)/15*(17719*j/50) - (j/16)*(15238*j/43) + 29
+	year = 30*n + j - 30
+	month = (24 * l) / 709
+	day = l - (709*month)/24
+	return
+}
+
+func ToISODate(t time.Time) string {
+	year, month, day := t.UTC().Date()
+	hYear, hMonth, hDay := GregorianToIslamic(year, int(month), day)
+	return fmt.Sprintf("%04d-%02d-%02d", hYear, hMonth, hDay)
+}

pkg/hijricalendar/calendar_test.go

@@ -0,0 +1,45 @@
+package hijricalendar
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestToISODate(t *testing.T) {
+	tests := []struct {
+		name string
+		date time.Time
+		want string
+	}{
+		{
+			name: "ramadan 3 1447",
+			date: time.Date(2026, 2, 20, 0, 0, 0, 0, time.UTC),
+			want: "1447-09-03",
+		},
+		{
+			name: "ramadan 1 1447",
+			date: time.Date(2026, 2, 18, 0, 0, 0, 0, time.UTC),
+			want: "1447-09-01",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := ToISODate(tt.date)
+			require.NotEmpty(t, got)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}
+
+func TestGregorianToIslamicRange(t *testing.T) {
+	y, m, d := GregorianToIslamic(2026, 2, 20)
+	assert.Positive(t, y)
+	assert.GreaterOrEqual(t, m, 1)
+	assert.LessOrEqual(t, m, 12)
+	assert.GreaterOrEqual(t, d, 1)
+	assert.LessOrEqual(t, d, 30)
+}

pkg/prayer/types.go

@@ -2,6 +2,7 @@ package prayer
 
 import (
 	"errors"
+	"time"
 )
 
 var ErrInvalidLocation = errors.New("invalid location")
@@ -19,16 +20,22 @@ type Location struct {
 	CountryCode    string  `json:"country_code"`
 	Latitude       float64 `json:"latitude"`
 	Longitude      float64 `json:"longitude"`
+	Timezone       string  `json:"timezone,omitempty"`
 }
 
 type Times struct {
-	Date        string `json:"date"`
-	DateIslamic string `json:"date_islamic,omitempty"`
-	Fajr        string `json:"fajr"`
-	Sunrise     string `json:"sunrise"`
-	Dhuhr       string `json:"dhuhr"`
-	Asr         string `json:"asr"`
-	Sunset      string `json:"sunset,omitempty"`
-	Maghrib     string `json:"maghrib"`
-	Isha        string `json:"isha"`
+	Date      time.Time `json:"date"`
+	DateHijri string    `json:"date_hijri"`
+	Fajr      time.Time `json:"fajr"`
+	Sunrise   time.Time `json:"sunrise"`
+	Dhuhr     time.Time `json:"dhuhr"`
+	Asr       time.Time `json:"asr"`
+	Sunset    time.Time `json:"sunset,omitempty"`
+	Maghrib   time.Time `json:"maghrib"`
+	Isha      time.Time `json:"isha"`
+}
+
+type TimesResult struct {
+	Location Location `json:"location"`
+	Times    []Times  `json:"prayertimes"`
 }