Filling data that includes midnight

When you get your data from the archive, it's normally in several files. For me, each file is usually a day's worth of data, so I fill and calibrate each data file separately. However, if you have observations that go from say 20:00 on 17-Feb to 6:00 on 18-Feb, the archive creates a separate files for the observations on the 17th and for the observations on the 18th. You need to read in both files to calibrate that series of observations.