Difference Between 2 Timestampl's

Hi experts,

I am trying to find the difference between 2 timestampl's in string form ('YYYYMMDDhhmmssmmmuuun'). Last time I posted people gave me ways to find the difference between 2 timestamps which is not what I want. I want the precision of timestampl. Last time I posted the post got removed by a moderator who might not have fully read/understood the question. If you can find me another question that has an answer for finding the difference between 2 timestampl's please let me know. Any help with this is much appreciated.

Thanks,

Bradley