Interval for add command detail's input

[tengcharmaine]

For your details input for your add command, I was able to key in any amount of time eg 365 days, 12 months, etc. Might be more user friendly if you can automatically convert for example 365 days into 1 year.

Additionally, some users might want to input a mixture of days, months, years for example 3 months 4 days but are not able to do so with the current implementation. Can consider allowing for multiple interval (day, month, year) to make it more flexible for users.