I agree that the date issue might be the confusing point. Really iNaturalist should have an accuracy or range associated with the temporal data in the same way as it’s associated with the spatial data.
This is a bit tangential, but since @bouteloua suggested a GIF, I may be able to offer a how-to suggestion that might help in making your observations.
I’ve found GIFs to be rather informative and since they can be uploaded on iNat, why not? Here’s an example that I uploaded of a giant water bug that I found on the sidewalk late one night. Individual screenshots were a little blurry, but collectively it’s very clear when animated:
Note: this was derived from a short video clip, but image series are essentially the same.
To make a good GIF, you ideally would not move the camera in any way, but this might not be feasible. One option that might work is to create a holder for the camera (perhaps out of cardboard, taped down or anchored to a particular spot) to ensure that it gets aimed the same way each time.
It can also be helpful to include some reference points that will be in the frame that might allow you to align the images in the future. And if you are going for high quality, some kind of colour reference may be in order, especially if the lighting, or even the coverage of a particular colour, changes substantially in the course of the experiment.
If you’re really feeling keen, a RaspberryPi with the associated small camera accessory can be set up to take photos at whatever interval you want - I’ve done this on a few research projects and it can work excellently. Plenty of guides are available online and it only takes a few lines of code to collect periodic images.
When you do have a series of images, it’s possible to import that series in FIJI (a version of ImageJ) as a “Stack”. A stack can be used to create a GIF or a montage. There are limits to the upload size on iNaturalist, so it’s often helpful to crop the GIF to only show the relevant area. It’s also possible to label the individual slices (images) within the GIF to show the date & time.
In any case, I’m curious to hear how your mold-observing experiment goes!