Converting from DateTime to Epoch – and back

I found the question about converting epoch time to normal time, but I’m having two problems:

  1. When I run DateTime.newInstance(1391529600 * 1000) I am getting the wrong answer
  2. I want to convert normal time to epoch time

1: I have been typing the following into Execute Anonymous:

system.debug(DateTime.newInstance(1391529600 * 1000));

By my calculations (and some websites I found) that should give me 4 Feb, 2014, 16:00:00 GMT.

Apex gives me

1969-12-31 12:56:36

Clearly, this is incorrect (and it’s even before 1/1/1970). Can anyone replicate my situation?

2: I also want to change the current datetime (GMT) to epoch time, returning the number of seconds or milliseconds since 1/1/1970. I could break things into parts, but that seems an awful lot of script statements to do something that should be fairly easy, I’d hope.

Thanks for the help!

Answer

I can replicate it, and by removing the * 1000 and appending 3 zeros, I got “Invalid Integer”. So what I believe is that 1391529600 * 1000 is being evaluated as an integer type and so overflowing.

You can create the Long value using the L notation like so:

system.debug(DateTime.newInstance(1391529600000L));

To get the epoch from a datetime variable you can just call the getTime() instance method:

Datetime dt = Datetime.now();
Long l = dt.getTime();
system.debug(l);
system.debug(DateTime.newInstance(l));

produces:

USER_DEBUG|[7]|DEBUG|1391560453900

USER_DEBUG|[9]|DEBUG|2014-02-05 00:34:13

Attribution
Source : Link , Question Author : DavidSchach , Answer Author : Community

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