Show the date and time when the picking ticket was printed

1. Navigate to  Customization > Lists, Records, & Fields > Transaction Body Fields > New. 
2. Enter the Label: Date Printed 
3. Select Date in the Type field dropdown. 
4. Do not check the Store Value checkbox. 
5. Check the Print on Picking Ticket checkbox under the Applies To tab. 
6. Select Main in the Subtab dropdown under the Display tab. 
7. Click the Validation & Defaulting tab and enter the formula in the Default Value field: to_char(sysdate,'DD-MON-YYYY HH24:MI:SS') or to_char(current_date,'mm-dd-yyyy hh:mm:ss')

8. Check the Formula checkbox under the Validation & Defaulting tab. 
9. Save.

Note: Date and Time formats should be set accordingly so that the custom field will work by navigating to Home > Set Preferences > General > Formatting:

1. Date Format: DD-MONTH-YYYY
2. Long Date Format: Month DD, YYYY
3. Time Format: hh:mm AM/PM