If someone rents an Airbnb for a few months in a new location are they now a resident of that new location? If we aren't talking about residency then changing an association (whatever that means) seems arbitrary.
But yes, those kinds of thresholds are common when it comes to residency as an official concept for e.g. taxation. Usually the threshold is around 183 days, but there is no reason why it'd be obviously less arbitrary than other choices.
But most importantly, it's the number that the US government uses on form 8840, the Closer Connection Exception Statement for Aliens: https://www.irs.gov/pub/irs-pdf/f8840.pdf
And know I know why, it's because US goverments uses this number as a cut-off for some legal consequences. Thank you!
> As someone who travels a lot (not recently!)
For the UK it's 31 days of more than 3 hours of work. I think it's the same for the US.
The Automatic Overseas Test
You would normally be considered a non-UK resident if you meet any one of the following elements of the Automatic Overseas Test:
You were considered as a UK resident in one or more of the previous three tax years, but you spend fewer than 16 days in the UK in the current tax year
You spend fewer than 46 days in the UK in the tax year AND you were non-UK resident in the preceding three tax years
You work full time outside the UK and spend fewer than 91 days in the UK and you work fewer than 31 days in the UK for three hours or less in any given day.