Zee, a community manager with Google, posted a thread at the Google AdWords Help forum on advertising tips with Google AdWords for Valentine's Day.
She explained that in 2011, people started searching for gift ideas for Valentine's Day on January 9th. In 2012, people began searching for gift ideas on January 7th. This year, in 2013, it appears searching started this behavior two day earlier, on January 5th. She showed a graph in Google Trends to show evidence of this:
Zee also added some tips and advice from other threads on how to best optimize your Valentine's Day AdWords campaigns. She said take a look at these two threads:
Forum discussion at Google AdWords Help.