What if I don't know the exact time of birth?
Leave the time blank. It is optional: without it the poster simply leaves the time out, and nothing else changes. On a design with the moon, the phase is worked out for noon on the birth date instead, and a few hours either way change the lit part of the moon by only a percent or two.
Updated October 9, 2026
What happens to the moon without a time
The lit part of the moon changes by at most about half a percent an hour, so a disc drawn for noon is within a few percent of one drawn for the minute your baby arrived, hard to tell apart on the wall. The phase name follows the almanac rule: if a full moon, a new moon or a quarter falls at any moment of the birth date, the poster names that phase, whatever the time. What does matter is the time zone, because it decides which calendar day the moon is worked out for. The form starts on Eastern time; pick another US time zone if your baby was born elsewhere.
If you only know roughly when
Only type a time you are happy to see printed: whatever is in the time field appears on the poster, next to the date and the measurements. An approximate time such as 7:30 AM is fine if that is how you remember it. If you would rather not print a time at all, leaving the field empty still gives you the right moon for the day. The preview shows exactly what the files will contain, so check it before you pay.
Related questions
Start with the name and date
Type them on the birth poster page and see every design with them. The preview is free.