Admittedly, it reeks of terse C

The current implementation also checks that it parses to something truthy, we'd need to further nest ifs to ensure parsing happens correctly, though we could pull the assignment out of the if condition.

if headers.expires doesn't exist we get
`if (Date.parse(undefined))` which is `if (NaN)` and NaN is falsey, also, if date is funky (i.e. not parseable as a date) we get `if (Date.parse("abc"))` which becomes `if (false)`