Questions about leave time calculation

First, let's talk about the leave rules: 1. for morning leave, the duration should not be less than 3 hours 2. for afternoon leave, the duration should not be less than 5 hours 3. working hours: 9: 00 ~ . There is one non-working hour at noon. due to the company's system, there is no overtime fee, but the time can be adjusted, so the time must be accurate to... first, let's talk about the leave rules:
1. leave in the morning for a period of no less than 3 hours
2. leave in the afternoon for a period of no less than 5 hours
3. working hours: 9: 00 ~
4. one non-work hour at noon
Because of the company's system, there is no overtime, but it can be adjusted, so the time must be accurate to the hour. The problem arises:
1. if the time span for my leave is from the morning to the afternoon to meet the rule, but the system computing time will be one more hour:

• My solution is: first determine whether the start time and the end time are the same day, then determine whether the start time is morning, and whether the end time is afternoon, then the system calculates the time minus one hour.

2. if some people are stupid, they have to determine whether to deduct the time after because the start time and end time have exceeded the working time. for example, the end time is after.

3. the most troublesome thing is cross-day, if the holidays include special circumstances such as statutory holidays and double vacations. There is also a non-integer cross-day, for example, please go to eleven o'clock A.M. three days after, then three days after ~ How can I remove it?

This is a bit confusing. please share your experience with experienced elders. thank you !!