Convert MSSQL timestamp to UNIX timestamp

Today I had to pull a number of datetime fields from MSSQL and update records in MySQL with them, using PHP.

The most efficient way to convert the date-time field to a unix timestamp for inputting into MySQL was the following:

DATEDIFF(s, "19700101", ro_job_date) as ro_job_date,

In this example the field was ro_job_date

19700101 is the 1st Jan 1970, the “unix epoch”.

I didnt have to convert from unix timestamp to MSSQL datetime, but researching the above turned up this snippet for that:

SELECT DATEADD(s, unix_timestamp, '19700101')

where unix_timestamp is your timestamp field