PostgreSQL to SQL Server Migration Error Caused by Default Value Expression
For "normal" (day, week, month, year, ...) in T-SQL you'd use the DATEPART function. (Check DATEPART (Transact-SQL)). However, this function doesn't deal with 'epoch'.

The definition of date_part('epoch'::text, now()) in PostgreSQL is: `time elapsed since the "epoch time" (1 Jan 1970), measured in seconds. In T-SQL, you would compute it with:

DATEDIFF(second,'19700101 00:00:00:000', getutcdate())