Is your feature request related to a problem? Please describe.
To limit the analysis to a couple of frames, we currently allow slicing as an array. However, it would be nice to provide a function that users can use to convert a time into the corresponding frame.
Describe the solution you'd like
convert something like "1ps" or "1 ps" or "5 ns" into the frame based on the timestep of the trajectory. There is already a helper function in mdacli that might be useful
https://github.com/MDAnalysis/mdacli/blob/99e34787e89a00e243c77cfe3f7826f08f119a38/src/mdacli/utils.py#L47
Describe alternatives you've considered
No response
Additional context
No response