How long after purchasing an apple watch do i have to buy apple care plus?

Hi

If AppleCare+ is available to purchase online for your Apple Watch, then it may be offered as an option when checking your service coverage here:

http://checkcoverage.apple.com/

Otherwise, to learn about any AppleCare+ policy or plan that may be available to buy in your country and the applicable time limit for purchasing it, follow this link, select your country and, on the next page, see the information within any section headed "Can I buy additional coverage for my Apple Watch?":

Apple - Support

Details for the US and UK, for example - including instructions at the bottom for buying AppleCare+ - are detailed here:

• US: AppleCare+ - Apple Watch - Apple
• UK: Apple Watch - AppleCare+ - Apple (UK)