# Sidereal Time

> Calculates local and Greenwich apparent sidereal time with NTP synchronization. (iPhone/iPad app by Milan Battelino.)

- Source: https://appshunter.io/ios/app/sidereal-time/id360770914 (this page in markdown: same URL + `.md`)
- Developer: [Milan Battelino](https://appshunter.io/developer/358569307)
- Category: Utilities, Education
- Price: $0.99
- Rating: 2.89/5 from 9 App Store ratings · 12 written reviews indexed
- Age rating: 4+
- Requires: iOS 8.0 · 1 MB
- Languages: English
- Released: 2010-03-10
- Data updated: 2026-06-10
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/sidereal-time/id360770914/reviews.md

## What is Sidereal Time?

The Sidereal Time App gives the user a simple and quick way to determine:

- Local Apparent Sidereal Time (LAST) based on longitude 
- Rough estimate of LAST based on Time Zone
- Greenwich Apparent Sidereal Time (GAST)
- Select one of 30 Stratum-1 NTP servers or add your own to synchronize the clock against the primary network time standard

The App uses core location (GPS, cellular triangulation and/or Skyhook Wireless's Wi-Fi system) to determine the users present position and hence his LAST. The user may also manually select the longitude coordinate to determine LAST or make a rough estimate by selecting a Time Zone. 

A running clock with the Coordinated Universal Time is presented in parallel with the Sidereal Time clock.

Local Apparent Sidereal Time at any location differs from the Greenwich Sidereal Time value of the same moment, by an amount that depends on the longitude of the location. When one moves eastward 15° in longitude, sidereal time is larger by one hour and hence wraps around at 24 hours. Unlike computing local solar time, differences in longitude and time are counted here to the accuracy of measurement, not just in whole hours.

## Key features

- Local Apparent Sidereal Time (LAST) calculation
- Greenwich Apparent Sidereal Time (GAST) display
- Longitude and Time Zone input
- NTP server synchronization
- Coordinated Universal Time (UTC) clock

## Recent user reviews (10 of 12)

All indexed reviews: https://appshunter.io/ios/app/sidereal-time/id360770914/reviews.md

### 1/5 — I have a vpn. App would not work. No mechanism to manually enter location.

*2021-01-07, version 1.7*

I have a vpn. App would not work. No mechanism to manually enter location.

### 3/5 — crashes in ios 14

*2020-11-10, version 1.7*

fails to launch

### 3/5 — Accurate calculation, but no night mode

*2019-11-28, version 1.7*

Straight-forward app for displaying times useful for astronomers, such as UTC and LAST, and does so correctly to better than 1 second accuracy!

Unfortunately, this suffers from a major problem: I cannot find a setting to display as a night-vision safe dim red, making this useless as a visual astronomy observation clock.

### 3/5 — Nice app

*2018-03-21, version 1.7*

Needs an alarm to alert when is your own sidereal time.

### 1/5 — No luck

*2015-11-05, version 1.6*

Apparently the download failed. I have OS X Yosemite 10.10.5 which I just learned does not support this app. Should not be offered in iTunes store. Regret wasting time with this.

### 1/5 — Unable to set.

*2014-08-03, version 1.6*

I just got this app and I cannot find any settings. I am only getting two clocks one for Greenwich Mean Time and one for Universal with no ability to get my local sidereal time. Am I missing something?

### 5/5 — Very Nice

*2012-03-14, version 1.6*

Great App!!!

### 4/5 — Nice App

*2011-07-01, version 1.6*

This seems to be a nice app. Simple, pleasing design, nice colors. But needs an alarm clock for sidereal time and a countdown clock without an alarm.

### 5/5 — Ntp won't stay locked on

*2011-04-06, version 1.6*

Would be nice if you could lock to selected Ntp server

### 5/5 — Works great!

*2010-08-12, version 0*

Very simple and a great value!

## Frequently asked questions about Sidereal Time

### What is Sidereal Time used for?

Sidereal Time is crucial for astronomy as it directly relates to the apparent position of stars in the sky. It's used in telescopes and observatories to track celestial objects accurately.

### How does Sidereal Time determine my location?

Sidereal Time uses your device's core location services, including GPS, cellular triangulation, and Wi-Fi positioning, to determine your current longitude for accurate Local Apparent Sidereal Time calculations.

### Can I manually set the longitude in Sidereal Time?

Yes, you can manually select the longitude coordinate to determine LAST or make a rough estimate by selecting a Time Zone if GPS is unavailable or you wish to calculate for a different location.

### How accurate is the time synchronization in Sidereal Time?

The app synchronizes its clock against primary network time standards by selecting one of 30 Stratum-1 NTP servers or allowing you to add your own, ensuring high accuracy.

### What devices is Sidereal Time compatible with?

Sidereal Time is available for iPhone and iPod devices. It was last updated to version 1.7 on September 25, 2017.

### What is the age rating for Sidereal Time?

Sidereal Time has an age rating of 4+, making it suitable for a wide range of users interested in its utility.

### How much does Sidereal Time cost?

Sidereal Time is a paid application, priced at $0.99. There are no in-app purchases or subscriptions mentioned.

### Does Sidereal Time have ads?

The provided data does not indicate the presence of advertisements in Sidereal Time. As a paid app, it is likely ad-free.

## Version history (last 1 release)

### 1.7 — 2017-09-25

This app has been updated by Apple to display the Apple Watch app icon.

Updated for iOS 11.0.
Minor bug corrections.

## Apps similar to Sidereal Time

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Rule of Three Calculator](https://appshunter.io/ios/app/rule-of-three-calculator/id1185318300) | 2.3 (4) | Free | Utilities |
| [レコーダー - スピークバディ パーソナルコーチング](https://appshunter.io/ios/app/id1469874020) | — | Free | Utilities |
| [TLF Events Tamil](https://appshunter.io/ios/app/tlf-events-tamil/id1481109080) | — | Free | Utilities |
| [ClockMaster - Time Regulator](https://appshunter.io/ios/app/clockmaster-time-regulator/id413901882) | 3.8 (52) | $49.99 | Utilities |
| [小灵龙App](https://appshunter.io/ios/app/app/id1221738240) | 1.0 (12) | Free | Utilities |
| [SSI Steel Design](https://appshunter.io/ios/app/ssi-steel-design/id1474838160) | 3.0 (1) | Free | Utilities |

## More apps by Milan Battelino

- [Julian Date Calculator](https://appshunter.io/ios/app/julian-date-calculator/id358569304)
- [Nine To Five](https://appshunter.io/ios/app/nine-to-five/id369690146)
- [Quick Feng Shui](https://appshunter.io/ios/app/quick-feng-shui/id424582751)
- [Tasbih Oracle](https://appshunter.io/ios/app/tasbih-oracle/id427812528)

All apps by Milan Battelino: https://appshunter.io/developer/358569307

---

*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-10.*