Read a line of text and set it as a variable for a batch file

I want to put a date/time in a line in a text file then have my batch file use that date to compare against the current date/time. How would I do that?

To define a windows variable from text in a file:

set MYVAR= type abc.txt

set is used to tell the computer to set a variable called my var and type abc.txt is the command to read a files contents.