Using the day number variable with or without leading zeroes:
Especially when used within the filename:

&QQ --> Number of the day in the year associated with the transfer identifier
&SYSQQ --> Number of the day in the year associated with the system date

These two variables are displayed without leading zeroes.

The leading zeroes may be needed, especially if those symbolic variables are to be used in the filename construction:
Following syntax must be considered:

&>QQ or &>SYSQQ

I.E.: For first day of the year this will give:

&QQ   = 1
&>QQ = 001 (leading zeroes not suppressed)