Calculator
Example data table
| Location | Date | Latitude | Longitude | Timezone | Sunrise | Sunset |
|---|---|---|---|---|---|---|
| Lahore Garden | 2026-02-25 | 31.5204 | 74.3587 | Asia/Karachi | 06:33 | 17:57 |
| Karachi Plot | 2026-02-25 | 24.8607 | 67.0011 | Asia/Karachi | 06:57 | 18:32 |
| Islamabad Beds | 2026-02-25 | 33.6844 | 73.0479 | Asia/Karachi | 06:41 | 18:01 |
Formula used
The calculator follows the standard sunrise equation used by many almanacs. It computes the Sun’s apparent position for the selected date, then solves the hour angle when the Sun reaches the chosen zenith.
- Zenith (Z) sets the solar depression angle. Official sunrise uses Z ≈ 90.833°.
- Hour angle (H) is found from cos(H) = (cos(Z) − sin(φ)sin(δ)) / (cos(φ)cos(δ)).
- Time conversion uses the equation of time and longitude to convert solar time to clock time.
- Elevation adjustment applies a horizon dip correction so higher sites see sunrise slightly earlier.
Practical note: weather, terrain, and nearby buildings can shift the “first light” you observe in the garden.
How to use this calculator
- Enter your garden’s latitude and longitude from a map app.
- Select the date you want to plan for, then confirm the timezone.
- Keep the official zenith for common gardening schedules.
- Optionally add elevation and twilight windows for low-light tasks.
- Click calculate to view results above, then download if needed.
Seasonal sunrise shifts and bed readiness
Sunrise can move by more than an hour across the year, even in mid‑latitudes. Use the selected date with your garden coordinates to anticipate earlier light for sowing, transplanting, and morning inspections. Day length in the results helps compare weeks and spot rapid change near equinox periods. At 25–35° latitude, a week-to-week shift of 2–4 minutes is common; near solstices it slows, near equinoxes it accelerates.
Irrigation timing and water loss control
Early watering reduces evaporation and wind drift. Scheduling irrigation within 30–90 minutes after local sunrise often improves soak depth while keeping foliage dry sooner. The calculator’s timezone and solar noon output help you avoid watering too close to peak radiation, when evapotranspiration demand is highest. If you use 12‑hour format, match it to your timer settings to prevent AM/PM mistakes.
Frost risk, dew point, and disease pressure
Clear nights can cool surfaces below air temperature, producing frost or heavy dew. If sunrise is late, leaves may stay wet longer, increasing fungal pressure on susceptible crops. Use civil twilight as a practical “first workable light” and pair it with a thermometer reading to plan covers, ventilation, or delayed pruning. Elevation can advance apparent sunrise slightly; the tool applies an effective zenith to account for this.
Pollinators, pruning windows, and low‑light work
Bees and many beneficial insects become active after temperatures rise post‑sunrise. For pollinator‑friendly practices, spray or dust outside the early activity window and avoid bloom disturbance. Twilight settings provide expanded low‑light periods for quiet tasks like trellis tying, harvesting, and drip checks without midday heat stress.
Logging, repeatability, and location comparisons
Exporting results to CSV or PDF supports weekly planning and documentation. Compare two plots by running the tool with each latitude and longitude; small longitude changes can shift clock time by minutes, while latitude can change day length significantly. Keeping a consistent zenith option improves repeatability across seasons.
FAQs
1) Why do I need both latitude and longitude?
Latitude controls the Sun’s path angle, while longitude shifts local solar time. Together they determine the hour angle when the Sun reaches the chosen zenith, producing accurate sunrise and sunset times for your exact plot.
2) What zenith option should gardeners use?
Use the official setting (about 90.833°) for standard sunrise and sunset planning. Choose civil twilight if you want the earliest usable light for setup, inspection, or travel time before bright sun arrives.
3) Why can sunrise differ from what I see outdoors?
Buildings, trees, hills, and haze can delay visible first light. Weather also affects perceived brightness. The calculator reports astronomical timing at your coordinates, so treat it as a planning baseline, not a visibility guarantee.
4) How does timezone selection affect results?
The tool converts solar calculations into clock time using the selected timezone and date-based UTC offset. This matters in regions observing daylight saving time, where the offset can change between seasons.
5) Does elevation really change sunrise time?
Yes, slightly. A higher viewpoint sees the horizon sooner. The calculator applies a horizon dip correction and reports an effective zenith, typically shifting times by seconds to a few minutes depending on elevation and terrain.
6) How should I store results for weekly routines?
Run the calculation for each planned date, then download CSV for spreadsheets or PDF for sharing. Keep the same zenith and timezone across runs so comparisons of sunrise trends and day length remain consistent.