Assuming 40-hour weeks and that you get credit for "work" on holidays (I don't know how long people are working, but if we're talking exempt employees the calcu

Assuming 40-hour weeks and that you get credit for "work" on holidays (I don't know how long people are working, but if we're talking exempt employees the calculation is probably based on a 40-hour week), you'd maximize that by starting 25 weeks from the end of the year. The 175th-to-last day of the year is July 10. So, yes, mid-July is the worst possible time to start from a 401k point of view.