This has been brought up a few times before, and the main reasons for eliminating second-level granularity are 1) it greatly helps reduce the amount of storage required for storing the program data, especially since OpenSprinkler supports up to 48 stations and 14 programs. 2) we did survey on the forum and pretty much everyone said they only need minute-level granularity. I am curious: how much water time are you setting for each station? Is it down to seconds?
Now that we have started moving more data to the microSD card, it’s possible to enable full precision again on the water time. We will look into this for future firmware upgrades.