"Before about 1918, surveyors would faithfully measure snow exactly on the first of the month, regardless of what day of the week it was. From 1919 to 1957, the surveyors would tend not to measure on Sunday, but didn’t mind going out on a Saturday if the schedule demanded it. Nowadays, if the first of the month is anywhere close to the weekend, the surveys are typically taken on the Thursday before (not even Friday). Today’s surveyors are three times less likely to work on a weekend than their predecessors. Certain sites have gone decades never measuring on a weekend. This reminded me of recent studies in the US and Australia showing how climate observers falsify recording zero without checking the gage if they think it didn’t rain. People often skip out of measuring on Sundays (reporting a zero), waiting until Monday to see what accumulated in the gage. People also like to record numbers divisible by 5 or 10, preferring to write down 0.45 inches even if the gage says 0.47."
Tom Pagano (The River Seers)