Date to Millisecond Calculators

Several date to millisecond calculators, useful when coding countdown timers, cookie expiration settings or other date related scripts. The calculators are coded in JavaScript.

If you need to do date math across timezones, follow this link to a couple date/timezone tools at the bottom of this page.

The known data:

Your computer's time:

-- the start of Unix Epoch Time
in your time zone ( ).

Convert a millisecond value to a date string

this (milli ) second time number: is the equivalent of this date string in time zone

Date to milliseconds converter

a date string
"Mon Jun 18 2007 00:00:00 GMT-0400"
or "09/23/2000"
or "09/23/2000 9:45:00"

What date would that be?

Your computer's time:
equals this date:

A temporal value converted to milliseconds

equals so many (milli ) seconds:

Milliseconds converted to a temporal value

So many (milli ) seconds: equals so many

How much time between now and then?

Your computer's time:

and this date:
"Mon Jun 18 2007 00:00:00 GMT-0400"
or "09/23/2000"
or "09/23/2000 9:45:00"

are so many apart:

How much time between now and then (using a millisecond date value)?

Your computer's time:

and this date in (milli ) seconds: are so many apart:

Date and Time Math Across Timezones

Date and Time Plus/Minus Quantity of Time

This date and time in timezone so many equals this date and time in this timezone

Date/Time Subtraction

This date and time in timezone minus
this date and time in timezone equals so many


  1. Thank you so much for building this! I’ve probably used this site over 100 times and its simply the best time calculator I’ve found anywhere. Real nice stuff!

    1. Hi Lee,
      If your phone is set incorrectly to a future date, as it appears to be from the image name: IMG_20181009_091252 (October 9 2018 or September 10 2018), and your phone created the picture, you may not be able to get the real original date.
      If the image name was created by some other device than the one that most recently named the file, you may be able to search through the image file’s EXIF data to see if it has a ‘date’ value. Here is a list of EXIF readers to consider for this task:

    1. Hi Roger,

      thanks for the info – very helpful. I think I’ve fixed the issue by updating to the latest versions of the moment.js scripts. These contain a fix that handles Timezone abbreviations specified in Chinese characters, which seems to be the case on computers set to the Hong Kong timezone on certain OSs.

      Please clear your browser cache and reload the page, and let me know how it goes.


  2. Moment Timezone 0.5.0 was already loaded with data from 2015g
    z @ moment-timezone.min.js:6

    Uncaught TypeError: Cannot read property ‘join’ of null

    1. Hi Roger,

      thanks for your help. Can you please help me by answering a few more questions:
      What value are you putting into the (milli)second time number field?
      Which timezone are you in?
      Which timezone are you setting in the form?
      Do you have any adblockers turned on? If so, what are you blocking?


    1. Hi Roger,

      I just tested it and it is working for me. I’ll look into the issue more if you can give me more info. Do you see javascript error in the console?


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