Void-of-course Moon
The Moon is void of course when it will make no further major aspect before leaving its current sign, a window traditional astrology treats as unfavourable for starting things.
The phrase is electional rather than natal: it describes a period of hours, not a placement in a birth chart. The classical advice is that nothing begun then comes to much, which practitioners read as a pause rather than a warning.
It ends the moment the Moon changes sign, which makes it one of the easiest classical conditions to time exactly.
Frequently asked
How long is a void period?
From minutes to most of a day, depending on when the Moon's last aspect falls before it changes sign.
Is it a bad time for everything?
Tradition limits the caution to beginnings. Routine and continuing work are not affected.