I was taught to leave the month off your start and end dates of previous positions when applying for a job. Still don’t know if this is a good idea or not, but at the very least it opens up another dialog tree with potential employers. Seems to have worked fine for me, but who knows. The rationale was “it’s less information to parse”. Might be just a superstition.

Interviewers always ask for more specifics anyways, which is good because you can use that as an opportunity to jump into things you accomplished near the end of a job, or at the beginning of another.