I have annual state panel data. Each state implemented a state reform at different times (year). I have information on the month and year of implementation. I want to generate a treatment dummy variable for the timing (year) of the reform implementation. I can generate a dummy variable equal to 1 or 0 by the year. However, in some cases like when the reform was implemented in November 2014, would the dummy receive a 1 in 2014 or a 0? Is there a way to create a dummy variable that would allow me to somehow capture the month in generating the dummy treatment variable? Note I don't have monthly state data, it is a panel of state annual data so I need to keep the year dimension in the data set.

Thanks in advance!
Marilyn