Cron has been extended to support 'last day of the month' and last week day of the month.

Lets recap the structure of a cron attribute:

cron -w<int_list> -d <int_list> -m<int_list>  <time>
time = single time slot *OR* time series 
int_list = comma separated integer list, see below for list of valid values

• -w day of the week  .   valid values are , 0 → 6 where 0 is Sunday , 1 is Monday etc
• -d day of the month,  valid values are in range 0-31
• -m month                        valid values are in range 0-12

Remember we *AND* across -w, -d, -m  then   *OR* for each element in -w, -d,-m

The new cron format will  use L,  to represent Last day of the month, or last week day of the month.

Hence we now support:

• -w day of the week  .   valid values are , 0 → 6 where 0 is Sunday , 1 is Monday etc AND
                                                                                    0L→6L, where 0L means last Sunday of the month, and 1L means the last Monday of the month, etc
                                                                                    It is an error to overlay, i.e. cron -w 0,1,2,1L,2L,3L 23:00  will throw an exception
• -d day of the month,  valid values are in range 0-31,L   Extended so that we now use 'L' to mean the last day of the month
• -m month                        valid values are in range 0-12

cron -w 0,1L 23:00                 # run every Sunday(0) and *last* Monday(1L) of the month at 23pm
cron -w 0L,1L,2L,3L,4L,5L,6L 10:00 # run on the last Monday,Tuesday..Saturday,Sunday of the month at 10 am
cron -d 1,L  23:00                 # Run on the first and last of the month at 23pm

The cron Late attribute can also be combined:  Remember we *AND* across -w, -d, -m or *OR* for each element in -w, -d,-m

cron -w 4L -d L 10:00             # run on the last Thursday(4L) of the month *AND Last of day of the month, this only occurs 3 times in a year in 2019
cron -w 0,1L -m 1 10:00           # run every Sunday and last Monday of the month, in January