Is the choice of St. Swithin's Day significant?

The book checks in on Dex and Emma every July 15, which is St. Swithin's day. Do you think the author's choice of this particular day is meaningful?

Except for the fact that it was raining the day of Emma's accident, which maybe suggested a bleak or "rainy" period to follow, I didn't really think there was much significance. Then, I read somewhere that St. Swithin's Day has a meaning in British slang of something that is not likely to ever happen, as in "He'll get around to doing that on St. Swithin's Day", or "never". If that's true, then it sets the tone for them not getting together. Or, maybe it means just the opposite. Every anniversary of St. Swithin's Day presents an opportunity for something to finally happen, or at least presents the chance for things to take a good or bad turn -- to have good or bad weather for 40 days.

I like the British slang interpretation--St. Swithin's Day meaning never.

The author also credits a song called St. Swithin's Day in the acknowledgements. (I won't paste in the lyrics here because of possible copyright infringement, but you can find them here: http://www.absolutelyrics.com/lyrics/view/billy_bragg/st_swithin's_day.)

It's a "love gone wrong" song, and the woman seems more interested in holding on to the relationship than the man. I'm not sure the song has any direct parallels with the novel, except for the general melancholy and "love doesn't last" theme.

I think the British slang certainly ties in nicely with the concept and title.

I agree that knowing the background of the phrase helps to tie everything together.