I want to store a paymentDate and renew the payment date with a given number of days.
ex: I have a struct called an agreement. assume it stores in a StorageMap. I want to modify the nextPaymentDate by adding 90 more days to the currently available date.
struct agreement{
id: u64,
nextPaymentDate: u64
}
How to achieve this? Be kind enough to change the data types if it is not suited to this work.