1st and 3rd number are for month or weeks?

[seahorseinstripes]

i see in some case it's read as the month and some read as the weeks?

can anyone help me understand this ?

thanks

 

[Nyria]

Prior to 2007 first and 3rd were months -- then starting in 2007 it became weeks.

 

[seahorseinstripes]

cool, thanks nyria