Other than to make the action move along, I can't remember there being an in-show/canon explanation for something they seem to say (a variation of) every episode of Timeless:
The mothership has just jumped, track it quickly, you guys prep for launch.
Why on earth do they need to hurry? They're literally about to use a time machine! So the mothership landed at 6am on Nov 9th 185x, land at 5:59am a mile away and off you go? Why do you need to hurry in the present?
The people I'm watching with had a couple of ideas:
- There's a risk that Flynn will change the timeline so much that you don't exist anymore (but surely he's already done that 100 years ago?)
- You can only go back years not days/hours
- You always travel back to the same time of day on a different date
- If you go back to before he lands he might choose not to land
Without an explanation though it just seems daft.