I've never used one of these DS3231 RTC chips but the datasheet makes this comment on the first page:only problem is that it dose not no about 28 days or 30/31 days in a month
I've never used one of these DS3231 RTC chips but the datasheet makes this comment on the first page:
"The RTC maintains seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year."
Your PICAXE program does not need to know about the number of days in a month. This is being taken care of by the DS3231 RTC chip.
As noted, a correctly set RTC will handle day and dates automatically. If you can explain what is not right, show the results you are seeing and indicate how that's different to what's expected, that may help identify what the issue is.