When the "Advanced" field is selected, you can use the text box to set your own date format, which would be displayed in MailBee WebMail Pro. The following options are used for this purpose along with ':' or '/' delimiter char:
Default date format
d
Day of month (1 through 31)
y
Day of year (1 through 366)
m
Month
q
Quarter
w
Day of week (1 through 7)
ww
Week of year (1 through 53)
yyyy
Year
For instance, if you've specified "m/d/yyyy" value in the text box of "Advanced" field, the date is displayed as month/day/year (i.e. 11/23/2005)