Hello:
A lot of my files have the year set as one of the following:
1977\\1977
2009\\2009-10-12
All I want is to have just the year, so the two examples here would have 1977 and 2009 as the year. I have tried all sorts of regex formulaes, and they either do nothing or clear everything.
thanks.
Hi and welcome 
It looks like the files have multiple year fields (you can inspect them individually via the extended tag dialog at Alt + T).
The easiest way to remove them is to use an action "Remove duplicate fields". See this topic for more on actions (in case it's needed).
Worked like a charm. Thank you very much Florian!