Weeks old would be the day (Tuesday) months old would be the date, for example my boy was born on the 7th of July so turned 2 months old on the 7th of September but was 9 weeks old the Sunday before
Date she was born in months and weeks to each week like my daughter was born 19thjuly she's 2 months today but 9 weeks tomorrow xx
On the date she was born rather than the day x