I'm trying to convert a C# DateTime variable to Unix time, ie, the number of seconds since Jan 1st, 1970. It looks like a DateTime is actually implemented as the number of 'ticks' since Jan 1st, 0001.
My current thought is to subtract Jan 1st, 1970 from my DateTime like this:
TimeSpan span= DateTime.Now.Subtract(new DateTime(1970,1,1,0,0,0));
return span.TotalSeconds;
Is there a better way?
I use year 2000 instead of Epoch Time in my calculus. Working with smaller numbers is easy to store and transport and is JSON friendly.
Year 2000 was at second 946684800 of epoch time.
Year 2000 was at second 63082281600 from 1-st of Jan 0001.
DateTime.UtcNow Ticks starts from 1-st of Jan 0001
Seconds from year 2000:
DateTime.UtcNow.Ticks/10000000-63082281600
Seconds from Unix Time:
DateTime.UtcNow.Ticks/10000000-946684800
For example year 2020 is:
var year2020 = (new DateTime()).AddYears(2019).Ticks; // Because DateTime starts already at year 1
637134336000000000 Ticks since 1-st of Jan 0001
63713433600 Seconds since 1-st of Jan 0001
1577836800 Seconds since Epoch Time
631152000 Seconds since year 2000
References:
Epoch Time converter: https://www.epochconverter.com
Year 1 converter: https://www.epochconverter.com/seconds-days-since-y0
UTC:
long timeSince1970 = DateTimeOffset.Now.ToUnixTimeSeconds();
Local time:
long timeSince1970 = DateTime.Now.Ticks / 10000000 - 62135596800;