There are many ways to interpret timing. The 12 days you mentioned would be from Swords equaling days and the Knight being the 12th card in the suit (if you count up from Ace).
If you're using a Golden Dawn influenced deck, then per the GD Astrological Associations
, the Knight Swords is Jan 10 - Feb 8. This Thread
has attachments with the associations from both Paul Foster Case and CC Zain.
Another way to look at the card is by the interpretation of the card. The Kn Swords can be about swift action, so the timing answer may be "when you're ready to take swift action."