Calendar popup bug in 2.53.10

[MondoV]

SeaMonkey wrongly displays a calendar popup as 6 days wide, whereas Chrome correctly displays it as 7 days wide.

In SM Nov 16 (today) is shown on a Friday (the 6th day); in Chrome, Nov 16 correctly falls on a Tuesday.

In Chrome, the popup is visually almost the full width of the data entry box (MM/DD/YYYY ... <calendar icon>) below it.

In SeaMonkey, the popup is visually approx 3/4 the width of the data entry box.

Error occurs on a real estate mgmt co's website trying to select a start date for auto-debit payts.

[MondoV]

Oops. Nevermind.
(Am new here. Prob should have posted the above in the SM Support forum/leg. Have since read lots of existing threads regarding things to look into and try.)
Ciao.