Regex for xx days, xx months or xx years

I need a regualr expression that accepts the following input

1 Day

4 Days

15 Days

1 Month

12 Months

1 Year

5 Years

The numbers may have any length. An开发者_开发技巧y ideas?

---

Try this,

^(1 (Day|Month|Year)|[1-9][0-9]* (Days|Months|Years))$

It will not accept what I assume is invalid input such as "5 Day" and "04 Months"

Explanation:

Either the input is "1 Day/Month/Year" or it is a digit 1-9 followed by any number of digits 0-9 followed by a space and one of the strings "Days" "Months" or "Years"

---

\d+\s+(Day|Month|Year)(s)?

• \d+ at least one digit
• \s+ at least one space character
• (Day|Month|Year) Day or Month or Year
• (s)? optionally pluralize the unit