client/lib/purchases/index.js
function maybeWithinRefundPeriod( purchase ) {
	if ( isRefundable( purchase ) ) {
		return true;
	}

	// This looks at how much time has elapsed since the subscription date,
	// which should be relatively reliable for new subscription refunds, but
	// not renewals. To be completely accurate, this would need to look at the
	// transaction date instead, but by definition this function needs to work
	// in scenarios where we don't know exactly which transaction needs to be
	// refunded.
	// Another source of uncertainty here is that it relies on the user's
	// clock, which might not be accurate.
	return (
		'undefined' !== typeof purchase.subscribedDate &&
		'undefined' !== typeof purchase.refundPeriodInDays &&
		moment().diff( moment( purchase.subscribedDate ), 'days' ) <= purchase.refundPeriodInDays
	);
}
function maybeWithinRefundPeriod( purchase ) {
	if ( isRefundable( purchase ) ) {
		return true;
	}

	// This looks at how much time has elapsed since the subscription date,
	// which should be relatively reliable for new subscription refunds, but
	// not renewals. To be completely accurate, this would need to look at the
	// transaction date instead, but by definition this function needs to work
	// in scenarios where we don't know exactly which transaction needs to be
	// refunded.
	// Another source of uncertainty here is that it relies on the user's
	// clock, which might not be accurate.
	return (
		'undefined' !== typeof purchase.subscribedDate &&
		'undefined' !== typeof purchase.refundPeriodInDays &&
		moment().diff( moment( purchase.subscribedDate ), 'days' ) <= purchase.refundPeriodInDays
	);
}
Checks if a purchase might be in the refund period, whether refundable or not.

If you need to determine whether a purchase can be programmatically refunded
via the WordPress.com API, use isRefundable() instead.

This function attempts to catch some additional edge cases in which a
purchase is refundable by policy but where isRefundable() returns false and
which would therefore require the assistance of a Happiness Engineer to
actually refund it.

The results aren't guaranteed to be reliable, so don't use them to promise
or deny a refund to a user. Instead, for example, use it to decide whether
to display or highlight general help text about the refund policy to users
who are likely to be eligible for one.

@param {Object} purchase - the purchase with which we are concerned

@returns {Boolean} Whether in refund period.