Find

Between dates

find / -newermt "27 Dec 2013" ! -newermt "1 Jan 2014"

-newermt newer than specified modification time
! invert proceeding condition

Several matches

find / -xdev \( -name .DS_Store -o -name ._.DS_Store \)

-xdev stay on the current filesystem
-o logical OR, use parentheses for clarity - must be escaped in bash