Survival Analysis - Account for heterogeneous time of entry with administrative censoring at year=T

I am new to survival analysis, although in the past weeks I have done my share of reading, hence this might be a non-problem. I have marriage and divorce data, spanning many years. I'm trying to model the causal change in hazard of divorce of a reform. A marriage is considered treated if it starts after the year of the reform, otherwise it is in the control group.

The year in which exposure to risk starts (i.e. the marriage year) is of course heterogeneous across individuals. Do I need to take this into account somehow? I am already controlling for year of birth and I am wondering if there's more I need doing, both from an identification perspective and from a technical one.

• PS: The reform I use affects only a part of the country of interest, while the rest of the country (i.e. of the individuals living in the rest of the country) is used as control group. So if there is a common time trend it should be accounted for. More precisely, given a 2001 reform of interest, an individual $i$ living in region $r$ and getting married in year $t$ is treated if r="treated region" & t>2001. He is not treated otherwise. – Fabio I. Jan 26 '19 at 0:46