If Possible, Don't Use Regex To Validate Numbers. If at all possible, use your language. There may be functions to help you determine if the value contained by a string is a valid number. That being said, if you're accepting a variety of formats (commas, etc.) you may not have a choice.
Type: match, Date: 7/12/2015 4:07:04 PMAuthor: stackoverflow
Use ([0-9]+) if you need to match more than one digit (only Arabic numbers!).
Use (\d+) if you need all digits (all unicode digits).
Type: match, Date: 7/12/2015 4:00:33 PMAuthor: stackoverflow
\d checks all Unicode digits, while [0-9] is limited to these 10 characters. For example, Persian digits, ?????????, are an example of Unicode digits which are matched with \d, but not [0-9]. [0-9] isn't equivalent to \d. [0-9] matches only 0123456789 characters, while \d matches [0-9] and other digit characters, for example Eastern Arabic numerals ٠١٢٣٤٥٦٧٨٩
Type: match, Date: 7/12/2015 2:34:00 PMAuthor: stackoverflow
Getting year from text.
If you want validate textbox value - use this pattern with "^" and "$":
^((19|20)\d{2})$
Type: match, Date: 3/28/2015 4:38:20 PMAuthor: admin
Using a RegularExpression to match web (HTML code).
Type: match, Date: 3/27/2015 4:21:44 PMAuthor: admin