# How to Calculate Stardates

Two Methods:Converting from Common Date to StardateConverting from Stardate to Common Date

Stardate is the dating system used in Star Trek. In the original series, they just made it up; so long as the next stardate was after the current stardate, it worked. Later on, it got a bit more serious.

## Steps

### Method 1 Converting from Common Date to Stardate

- 1
**Understand how long a year is.**There are 1000 stardate units in one Earth year. - 2
**Look at how long your year is.**365 days normally, 366 for a leap year. This number is called**n**. - 3
**Choose a base date.**The base date will determine all of your other calculations. There are two base dates that you can use: 2005 = 58000.00 and 2323 = 00000.00 The standard year (2005 or 2323) is now called**b**and the stardate year (58000.00 or 00000.00) is called**c**. - 4
**Calculate the "month number".**This number shall be called**m**. Here's a list: January = 0; February = 31. For all other months, add one if it is a leap year. March = 59; April = 90; May = 120; June = 151; July = 181; August = 212; September = 243; October = 273; November = 304; December = 334. - 5
**Find the day and year.**The day in the month is called**d**, and the year is called**y**. So, using 2005 as the base date, 23 May 2008 has these values: n = 366; b = 2005; c = 58000.00; m = 121 (120, +1 for leap year); d = 23; y = 2008. - 6
**Put these values into the formula.**The stardate formula is this: c + (1000*(y-b)) + ((1000/n)*(m + d -1)) = Stardate. Using the above values, the stardate works out to be 61390.71. Stardates are usually quoted to two decimal places.

### Method 2 Converting from Stardate to Common Date

- 1
**Know the base date that has been used.**As an example, lets look at the stardate from the last method, 61390.71. The base date is 2005 = 58000.00 - 2
**To calculate the year, look at the thousands (and above) digits.**Ignore the hundreds and tens (and units and decimals). In this example, you get 61000. - 3
**From this number, subtract the stardate base date, divide by 1000, and then add the common base date.**61000-58000 = 3000. 3000/1000 = 3. 2005 + 3 = 2008. This is the year. - 4
**Determine if it's a leap year.**A year that divides by four but not 100 is a leap year. A year that divides by four and 100 but not 400 is not a leap year. A year that divides by four, 100 and 400 (e.g. 2000) is a leap year. 2008 will divide by four but not 100, so it is a leap year. - 5
**To calculate month and day, look at the hundreds digit, and the lower digits.**Ignore the thousands and anything higher. You get 390.71. - 6
**Multiply by 365 (366 for leap years).**When you multiply 390.71 by 366, you get 142,999.86. - 7
**Divide by a thousand, then round to the nearest whole number.**142,999.86/1000 = 142.99986. Round up to 143. - 8
**Add one.**You get 144. - 9
**Determine the largest month number that can be subtracted from this number.**This number will be the month. Remember to add one to the month number if it's a leap year (and after February). The largest month number that goes into 144 is 121, so the month is May. - 10
**Subtract the month number to get the date.**144-121 = 23. So your date is 23 May 2008. That's correct, it's the day you started with.

## Warnings

- When converting stardates back into common dates, you may (not often) be a couple of days out due to rounding errors.

## Article Info

Categories: Astronomy