"EOF" is made up of entirely valid base64 characters, it would be bad if the program crashed because we tried to diff a file whose base64 representation contained the string EOF. underscores don't appear in base64 strings
relying on an interval causes the process to never exit, because the interval is still running in the background. this is bad for oneshot scripts like ours. instead the check works by comparing the current date to the last known date any time a post request is sent
