UTC millisecond Cast DateAdd Hours error

Don't cast as date, because date doesn't have hours:

CAST(DATEDIFF(SECOND, '19700101', DATEADD(hh, -3, GETDATE())) AS bigint) * 1000

I don't understand?

How should I write this?

WHERE [TimeStamp] < DATEADD(ms, -10800000, GETUTCDATE())

Now I don't understand.  Is TimeStamp a true datetime column or it elapsed ms since 1970-01-01 (unix style date)?

If it's a datetime, then, yes, I would think your last style of code would be right.

The TimeStamp is UTC milliseconds.  I do not have this working yet.  The error is "Arithmetic overflow error converting expression to data type datetime"

This is the first time I've worked with UTC and you can tell I just don't get it.  Yes - Is TimeStamp a true datetime column or it elapsed ms since 1970-01-01 (unix style date)?

Please help - this is the last piece to put this to bed.

elapsed ms since 1970-01-01 (unix style date)

Please

here's my current attempt

WHERE TimeStamp >=  CAST(DATEDIFF(SECOND, '19700101', DATEADD(hh, -3, CAST(GETDATE() AS date))) AS bigint) * 1000

Select allOpen in new window

The datepart hour is not supported by date function dateadd for data type date.
The statement has been terminated.

This project is a 60 day sprint with a $$bonus if I complete on time.  To say I'm a little ragged right now is an understatement.  Sorry for making a mess of this one!

I've got it working now - I think!  Notice the <= instead of >= and also I had to compensate for my server's location in -5 UTC zone.

WHERE TimeStamp <=  CAST(DATEDIFF(SECOND, '19700101', DATEADD(hh, -8, GETUTCDATE())) AS bigint) * 1000

Select allOpen in new window

Thanks