A prototype document did not have multiple entry dates or a number of months of service for eligiblity so a sponsor used 1.5 years. I haven't seen that - fractional years - and although it seems workable, does anyone see anything inherently wrong with it?

not sure I understand the situation. They used 1.5 years waiting period for eligibility, and then entry was exact date that waiting period ended? So if someone was hired 2/17/05, they entered the 8/17/06?

Sorry. Entry date is first day of the year nearest completion of 1.5 years of service

Standardized or non-standardized prototype? Also look carefully at the adoption agreement because many of them state what the default will be if no choice is made.

"Entry date is first day of the year nearest completion of 1.5 years of service"

so if someone was hired 2/17/05, they wouldn't enter until 1/1/07?

I don't think that's ok. My understanding is that there is a rule out there that essentially says you cant keep eligible people out of the plan longer than a year and a half after their hire date (unless you're doing the 2 year/ 100% vesting thing). The above example person would be forced to wait 1 year 10 months and 15 days.

And if they are immediately vested?

Assuming the document language works, I think it is OK if they are fully vested. See 410(a), 2 YOS substitutes for 1 YOS. So just like you can have a plan with a 6 month wait because it does not exceed 1 YOS, with full vesting you can have 18 months because it does not exceed 2 YOS.

I have not done this, so haven't looked at the regs for this issue to see if they create a problem, just commenting based on what 410(a) say.

This is either a profit sharing or Money Purchase, right? It would not be legal if it was a 401(k) Plan.