Dazmond rescheduling work means you haven't got it done .i do my work 4 and 8 weekly . And always pull work forward and catch it back up when needed .the main reason I believe 4/8 weekly is better than calendar month . . Resulting in all the 4 weeklys getting cleaned 13 times a year ,and the 8 weeklys 6 or 7 times a year . I believe you work calendar month ., so how do you leave it until January if it was due in December . Surely that is one calendar month clean missed for you . Not having a pop just curious how you manage that without losing money . 
cheers barry .
I now work this way from Dazmonds posts. Yes, your only giving 12 cleans a year but it gives 4 weeks where holidays/time off can be seen by looking at a yearly calendar.
It's still worked over 4 weeks (not 4 weekly) with the first Monday of the month being my start date.
Customers soon learn they are the fall due on the first Wednesday or whatever and saves me sending texts.
Round software copes with this system and it works for me.
Tony