More and More Daylight

It feels like the days here are much longer, already. There’s a reason for that, because during this time of year, the amount of daytime hours is increasing most rapidly. So it’s not just optimism — sunset really is noticeably later each week.

In December and June (around the solstices), the sunrises and sunsets happen at about the same time every day. In March and September (around the equinoxes), the sunrises and sunsets are changing rapidly.

Here’s a graph of the hours hoursdarknesssm.pngof darkness for Dublin throughout the year. The color indicates the rate of change in this number, so the fastest change occurs in the two yellow sections. For example, from December 1 to January 31, the number of hours of daylight changes by less than 50 minutes. On the other hand, from February 1 to March 31, the number of hours of daylight increases by almost four hours!

Not only that, but the greatest acceleration in the number of hours of daylight occurs weeks before the March equinox. In the first week of February, the speed at which sunset is moving later in the day is, itself, at its fastest for the year. (The illustration above, and much much more, appears in my forthcoming book, Calculus for Ex-pats).

The upshot is that it is supposed to feel like there’s a lot more daylight. (As a math teacher might say, your subconscious is doing calculus automatically.) And thank goodness for that. Anita and I managed to be out of town for most of the darkest weeks in Dublin, but what we saw was plenty for us.

The one caveat — and the one caveat that caught me every time in Chicago — is that the air temperature doesn’t necessarily follow this pattern. In Chicago, your sun-tracking-calculus-spidey-sense says that spring is coming in February. As we all know, there are many more weeks of crappy weather to go. The disconnect between sunshine and warmth would leave me despondent in early April. We’ll let you know whether spring works the same way in Dublin.

1 Comment to “More and More Daylight”

  1. Dave said...
    11 February 2008

    I’m glad you’re getting more sunlight. That’s the worst part of the winter, leaving before the sun comes up and getting home after it sets… I’m sure that spring will be unfulling in Dublin, given that your weather tracker says it’s 54 degrees there today. It was 2 degrees on my car themometer on my way in today. So if it warms up to 65 in both places, I’ll think it’s time to go sunbathing, and you’ll feel like it’s 65 degrees.