# Julian Date Calculator

> Converts Gregorian dates to Julian dates and multiple other time systems. (iPhone/iPad app by Milan Battelino.)

- Source: https://appshunter.io/ios/app/julian-date-calculator/id358569304 (this page in markdown: same URL + `.md`)
- Developer: [Milan Battelino](https://appshunter.io/developer/358569307)
- Category: Utilities, Education
- Price: $0.99
- Rating: 4.00/5 from 3 App Store ratings · 3 written reviews indexed
- Age rating: 4+
- Requires: iOS 8.0 · 2 MB
- Languages: English
- Released: 2010-02-27
- Data updated: 2026-06-10
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/julian-date-calculator/id358569304/reviews.md

## What is Julian Date Calculator?

The Julian Date Calculator gives the user a simple and quick way to convert between Coordinated Universal Time (UTC) in the Gregorian Calendar to the Julian Date as well as the following selection of additional epochs and time systems:

- Modified Julian Date
- Modified Julian Date 2000
- GMAT Modified Julian Date
- Reduced Julian Date
- Truncated Julian Date (NIST and NASA)
- Dublin Julian Day
- Lilian Day Number
- ANSI Date
- Rata Die
- Unix Time
- RAMSES Time
- GPS Time

The Julian date (JD) is the number of days and fractions of a day since noon January 1, 4713 BC at Greenwich. The Modified Julian Date (MJD) has an offset of 2,400,000.5 days from the Julian Date and hence starts at midnight November 17, 1858. The Julian Date is often used for scientific time measurement by the astronomy community and was introduced to provide a single system of dates that could be used when working with different calendars.

## Key features

- Julian Date conversion
- Modified Julian Date
- Truncated Julian Date
- Unix Time conversion
- ANSI Date
- Lilian Day Number

## Recent user reviews (3 of 3)

All indexed reviews: https://appshunter.io/ios/app/julian-date-calculator/id358569304/reviews.md

### 4/5 — Works well, but…

*2024-02-22*

The “PING!” When you update the current time is earsplitting. Make that so I can turn it off and you’ll get a ***** review from me. That’s five stars, not cursing, by the way.

### 3/5 — Very Limited Usability

*2022-12-18, version 1.6*

18 Dec 2022

I was hoping for a much better calculator with cleaner and better functionality than just being able to enter a date an time to get JD or any other time format.  The value add that is missed here are:

(1) The ability to enter current local rime without having to compute the UTC.  It’s a calculator and that is very basic functionality.

(2) The ability to be able to copy any field so that it can be pasted to a user’s astronomy log and/or observations made for AAVSO.  

Nine years after the original app was offered and at least these two things should have been incorporated.  I can only give it three stars at this point.  It is time to correct the basic functionality that should have been there all along.

### 5/5 — Works very well on iPhone5

*2013-07-30, version 1.5*

It would be perfect for me if it would have three more functions:
- Display a third UTC seconds "wheel"
- Allow entry and display of GPS time in hexadecimal notation
- display current leap-seconds. That display could display number in effect when displaying historical time, or disappear when not displaying current time. 
With those changes it would be worth more than $0.99 to me.

## Frequently asked questions about Julian Date Calculator

### What is the Julian Date Calculator?

The Julian Date Calculator is a utility app that converts Coordinated Universal Time (UTC) in the Gregorian Calendar to the Julian Date and several other time systems like Modified Julian Date, Unix Time, and ANSI Date.

### What is the Julian Date?

The Julian date is the number of days and fractions of a day since noon on January 1, 4713 BC at Greenwich. It's widely used for scientific time measurement, especially in astronomy.

### What is the Modified Julian Date (MJD)?

The Modified Julian Date (MJD) has an offset of 2,400,000.5 days from the Julian Date, starting at midnight on November 17, 1858. This app can convert to MJD.

### What other time systems does Julian Date Calculator support?

Beyond Julian Date and Modified Julian Date, it supports Modified Julian Date 2000, GMAT Modified Julian Date, Reduced Julian Date, Truncated Julian Date (NIST and NASA), Dublin Julian Day, Lilian Day Number, ANSI Date, Rata Die, Unix Time, RAMSES Time, and GPS Time.

### How much does Julian Date Calculator cost?

The Julian Date Calculator is a paid app, priced at $0.99.

### What devices is Julian Date Calculator available on?

Julian Date Calculator is available for iPhone and iPod.

### How often is Julian Date Calculator updated?

The latest version, 1.6, was released on September 25, 2017. The app was originally released on February 27, 2010.

### What is the age rating for Julian Date Calculator?

Julian Date Calculator has an age rating of 4+, making it suitable for a wide range of users.

## Version history (last 1 release)

### 1.6 — 2017-09-25

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

Updated for iOS 11.0.
Added:
- Modified Julian date 2000: Its initial epoch is at noon (12:00) proleptic Coordinated Universal Time (UTC) on January 1, 2000. It is commonly used in the space industry.
- GMAT Modified Julian Date: Its initial epoch starts at noon (12:00) proleptic Coordinated Universal Time (UTC) on January 5, 1942. It is used in the General Mission Analysis Tool developed by NASA.
- Leap seconds introduced June 30th 2015 and December 31st 2016

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## More apps by Milan Battelino

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

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*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.*