Legacy system and dates- what date is '733473'

Question

I am working with a legacy system whereby it seems they store dates as integers, such as 733473. Anyone seen this format before and can think of the logic to turn this into a date? It appears to be a day number, but not sure how many days from what date!

Edit: the value I get for 01/01/2013 is 734869. It is the amount of days since 0 i believe, but does this have a name? I need to write/find a native function in MSSQL server to convert these.

Answer 1

You are most likely correct, it's the number of days since Jan 1, year 0000 (or possibly 1).

$ date -u -d "0000-01-01 + 733473 days"
Fri Mar  7 00:00:00 UTC 2008

However, without knowing the date it actually corresponds to, we can't know for sure which leap year system it follows.

Answer 2

OK not sure the name of this date type (if there is one), but the below works:

declare @dt datetime2 = '00010101'
declare @int int = 734869

select dateadd(day,@int-1,@dt)

2013-01-01 00:00:00.0000000