This conversion looks close to what you want:

select

*,

MyDateTime =

dateadd(mi,convert(bigint,a.MyTime-998799780)%convert(bigint,1440),dateadd(dd,(a.MyTime-998799780)/1440,0))

from

( -- Test Data

select MyTime = convert(bigint,1056915413)union all

select MyTime = 000001056915413+(00000000001440*2918000)

Results:

MyTime MyDateTime

--------------------- -----------------------

1056915413 2010-07-01 01:53:00.000

5258835413 9999-09-17 01:53:00.000

Edit:

Changed solution to modify time offset, and to cover the entire range of DATETIME values.