I have the below search in one of my dashboards. I have a mutiselect field in my dashboard: one for picking the start date/time and another for end date/time. When i select multiple date/time, I'm getting only results for last selected values, it's not coming for multiple times selected.
The short answer is that earliest= can only accommodate one value, and so can latest=.
If you want to run multiple simultaneous searches for different time periods, then you are going to have to do a lot of custom code to make it happen (for example, setting up your searches using map or multisearch), not just straight-out-of-the-box multiselect for some time fields.
For example, see the final answer ( multisearch ) in this question