Consider adding convenience to processing and outputting date and time

[sakuraehikaru]

• We often have to write numerous helpers to process and output date and time strings
• Server APIs also tend to require and return date formats inconsistently
• Simple arithmetics on days, months, and years are also somewhat common right before, or in-between network requests, and we've had to use other libraries or write extra code just to do these
• Setting, tracking, maintaining, and converting to the correct timezone where needed is often a loosely handled programming process (at least to me), so it'll be nice if Netable has a design that helps make this process more transparent and easier

[jenncoop]

We might be able to use property wrappers to handle this instead of including it in Netable