If you're working as an employee, your employer is required to send you a W - 2 form by the end of January in following the tax year. (turbotax.intuit.com)
The law prescribes a time limit for making the election - 31 January following the tax year in which the charge arose. (politics.co.uk)
Contributions follow the tax year instead of the calendar year, so you have until tax day in mid-April to contribute to last year's contribution window. (rothiraAccounts.info)