"The Phoenix lander has operated at a Martian arctic site for more than two months longer than its initially planned, three-month prime mission. The sun stayed above the horizon around the clock during the prime mission, but is now below the horizon for about 7 hours each night."

And when we reach Mars' autumnal equinox, there will be slightly more than 12 hours of night [and slightly more than 12 hours of daylight] and the Sun's angle at noon will be about 23 1/2 degrees above the horizon.

"Phoenix landed in the Green Valley of Vastitas Borealis on May 25, 2008,[24] in the late Martian northern hemisphere spring (Ls = 76.73), where the Sun will shine on its solar panels the whole Martian day.[25] By the Martian northern Summer solstice (June 25, 2008), the Sun will appear at its maximum elevation of 47.0 degrees. Phoenix will experience its first sunset at the start of September 2008."
http://en.wikipedia.org/wiki/Phoenix_spacecraft

It would then be somewhat like being at earth's arctic circle at the the fall's equinox [September 22 or 23], though of course the sun would have 60% less energy.
Since Mars' year is twice ours, it should be a couple months before Mars' autumnal equinox.