.Net System.DateTime.Ticks has 10,000,000 ticks per second and starts from 0:00:00 UTC on 1 January 0001, in the Gregorian calendar. To get this number in SQL is quite complex but here is a shortcut:
This select statement calculates the .Net ticks in SQL and is accurate to the nearest second.
This is how I constructed the formula, first I got the ticks up to 2000 from powershell as follows:
Then I calculate the difference in seconds since 2000 and the current date and multiply the number of seconds with 10 million to get it into ticks.