Break in Service - Rehire

I often find it confusing to determine eligibility for rehired employees. The plan’s eligibility conditions are age 21 and 1 year of service, with a monthly entry cycle. The rule of parity does not apply.

Employee A was hired on 4/14/2022, terminated on 9/08/2022, and completed 590 hours. The employee was then rehired on 10/03/2023. If rehired 07/09/2023 what is the case of determining eligibility.

In this situation, should eligibility be calculated from the original hire date or from the rehire date?

Could someone also explain, with examples, how eligibility is determined for rehired employees who rehired within one year versus after one.