Convert int to datetime in SQL

I would start by looking at the code that generates the value - and by hunting down the developer who thought it was a good idea - and working out how a date is converted to that in the first place.

It looks like it's a number of seconds since a fixed time in the past which would be sensible if a DateTime in SQL wasn't stored as a number of ticks since 1753-01-01 00:00.0000 and a tick wasn't 0.00333 seconds. Sort of - it's stored as two separate counts in two 4 byte integers, one signed for the days offset and the other unsigned for the time offset.

If you can't find the code, then work out what the start date and time is, and go from there.

29.04.2016 23:07 is equal to 42487.9631944444 
The query is converting float to datetime is
SELECT CAST(42487.9631944444 as dateTime)
and converting datetime to float is
Select (CONVERT(float, CAST('04-29-2016 23:07 ' AS DATETIME)))

Msg 8115, Level 16, State 2, Line 5
Arithmetic overflow error converting expression to data type datetime.