while working around reading in values from an epw file for gendaylit for climate based simulation, I found some really weird time values in my data. The epw file should contain hourly data from 01:00 to 24:00. However, I found that the "minutes" field was set to 60 for every record, so the last record was 24:60. I tried to figure out what this could mean (I was first guessing that the timezone may have been applied by adding 60 minutes).
In the end, I got an answer that was rather surprising to me, and that I would like to share. The value "60" in the minutes field does NOT refer to the time when the measurement was recorded, but to the recording interval (hourly). In other words, it has nothing to do with the time stamp, but is an integration time. So 24:60 is the value for 00:00, and, if I understand this correctly, the values of the record should be the average of measurements from 23:30 to 00:30.
For using the data with gendaylit, this means that I sed the minutes fields and set it to zero (without incrementing the hours field). Did anyone else get stuck with this before? I hope I got it right now...