improve temporal module

[JessicaS11]

The temporal module was introduced (#327) to enable a broader range of temporal input types (beyond strings, including datetime object types) and streamline the time-handling portions to their own module. As always, there is more work that can be done to make it even better:

• [ ] simplify the module overall (perhaps to manage input datetime types (strings, datetime objects) independently of how they're entered (list, dict, kwarg))
• [ ] parameterize the testing module
• [ ] make the testing module more complete to test all possible input cases