This is the period starting from one date (normally the date of a notification) to the same date in the following month less one, or if that date does not exist in the following month, the last date in that following month. In both instances, allow for days when the office is not open for postal deliveries
Months on the calendar e.g. January, February etc. The calendar months are generally longer than 4 weeks
A Calandar Month is the period of duration from the same date of one month to the same date of the next month, and thus can be 28, 29, 30 or 31 days long. For example the duration from 21st January to 20th February.