The cp command annoys me sometimes in that i expect my files to retain their time-stamps. However, such is not the default. To set this behavior automatically, aliases may be used.
In a Linux ~/.bashrc file, include the follwing alias:
alias cp="cp --preserve=timestamps"
In an OSX ~/.bash_profile, include the following alias:
alias cp="cp -p"
In both cases you will need to exit and restart bash.