[1.55] TWAP: year and month calculation is not very precise

[elena-zh]

Related to #3568

Total duration counts a year as 365 days without consideration of the leap year.
Average month is also calculated as 30.3 days.
So when Total duration is converted into days, it is not very precise:

1. leap year shows 1year+1 day, however, part duration shows a correct division. The warning says that duration is too long, however, '6 month' in the part time is less than '6 m 12 hours' in the warning
   

2. regular year: part is calculated as 6 months and 12h, when in fact it's 182d + 12h (or 6 months)
   

Expected: values should be precise, values on the warning should match the value in the Part duration field.