Timezone adjustment for sites that report in daylight savings time

[lindsayplatt]

I tried to account for timezone differences between standard time and daylight time so that our daily values would be averaged using the correct date-times for each site's own timezone. Turns out that most of the sites in NWIS are reported in standard time already, so my shift from DT to ST was actually moving them earlier by an hour (see comment here). However, I discovered that this is not the case all the time and there are some sites that still report in daylight time (see this comment and code). Since fewer sites report in DT some of the time than standard time (only 76 vs 800ish), I kept my change in the code and am not doing anything else further for now because it is just a single hour, so it doesn't make a big difference in the averaged values and we are just dropping that one value that is not in the requested range.

This issue is a reminder to return to implement a solution for those sites that still do the switch. Maybe have some special list or way of determining whether they switch or not? Maybe it isn't even worth figuring out a solution.