i think you’re filtering by observed date rather than created date (which is what loarie is using).
interestingly, the two date range filters seem to work completely differently on the Explore page. if you filter by date added range, i think you’ll get back observations created between 12AM UTC on the from date and 12AM UTC on the to date. however, if you filter by date observed range, i think you’ll get back observations observed on the from date at local time of the observation (starting from the beginning of that day) through the to date at local time of the observation (to the end of that day).
in other words, if you want to filter by the week starting 2020-04-20 based on date added at UTC, the closest you can get is to filter by created_d1=2020-04-20 (Monday) and created_d2=2020-04-27 (Monday), though this will also bring back records created at 12AM UTC on 2020-04-27. but if you want to filter by the week starting 2020-04-20 based on observed date at local time, then you would filter by d1=2020-04-20 (Monday) and d2=2020-04-26 (Sunday).
i wasn’t expecting such a difference in the way the 2 sets of date filters worked, but it might reflect the fact that date added is more standardized since it’s determined by the system. (not sure.) i also wasn’t expecting that the histogram endpoint would start its week on a Monday as opposed to a Sunday.