Modify regex to take h:mm time format in addition of hh:mm

Question

I have this regex

^(1[0-2]|0[1-9]):[0-5][0-9]\040(AM|am|PM|pm)$

and it validates this time format: hh:mm AM|am|PM|pm, for example 04:25 pm, 11:20 am

How do I make 4:25 pm (no 0 before 4) be also valid? in other word make h:mm be valid time format in addition of hh:mm Please explain so I can understand what you do. Thanks!

`DateTime.TryParseExact` with `"h:mm tt"`. Implement your own validator. Do it [as it should be done](http://stackoverflow.com/questions/32624800/swedish-ssn-regular-expression-reject-users-under-a-specific-age/32625321#32625321). Regex is not your friend with datetime validation. — Wiktor Stribiżew, Sep 17 '15 at 23:03
Are you interested in a proper (non-regex) approach? If yes, post the relevant code. — Wiktor Stribiżew, Sep 17 '15 at 23:13

score 1 · Accepted Answer · answered Sep 17 '15 at 22:58

1

Try this:

^([1-9]|1[0-2]|0[1-9]):[0-5][0-9]\040(AM|am|PM|pm)$

answered Sep 17 '15 at 22:58

Reza Aghaei

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Why not `^(1[0-2]|0?[1-9]):[0-5][0-9]\040(AM|am|PM|pm)$`? – Gildor Sep 17 '15 at 22:59
please explain the whole regex, break it into each piece, could you? – Ronaldinho Learn Coding Sep 17 '15 at 23:01
@RonaldinhoLearnCoding | stands for OR So if you enter 1,2,3,4,5,6,7,8,9 OR 10,11,12 OR 01,02,03,04,05,06,07,08,09 the time part is correct. Also you may know, [1-9] means one of digits from 1 to 9. – Reza Aghaei Sep 17 '15 at 23:06
@Gildor why not, very good. I just typed what it came to my mind . – Reza Aghaei Sep 17 '15 at 23:14
@RezaAghaei Heelo Reza can you make am/pm be case insensitive, in other word it will accept: AM, Am, am, aM and same for PM – Ronaldinho Learn Coding Sep 18 '15 at 19:09
@RonaldinhoLearnCoding `^(1[0-2]|0?[1-9]):[0-5][0-9]\s([aA]|[pP])[mM]$` – Reza Aghaei Sep 19 '15 at 15:38
@RonaldinhoLearnCoding What was the result of test? Was it helpful? – Reza Aghaei Sep 19 '15 at 20:35

score 1 · Answer 2 · answered Sep 18 '15 at 20:52

Here is a non-regex way to write a DateTime validation in MVC app:

[Required(ErrorMessage = "This value is required!")]
[MyValidateTime]
public string TimeValue { get; set; }

And here is the MyValidateTime code:

public class MyValidateTime: ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {                 
        DateTime dt;
        if (DateTime.TryParseExact((string)value, new[] { "hh:mm tt", "h:mm tt" }, CultureInfo.InvariantCulture, DateTimeStyles.None, out dt))
            return ValidationResult.Success;
        else
            return new ValidationResult("Correct time formats: 01:00 AM or 1:00 AM");
    }
}

Here, the allowed time formats are:

hh:mm tt (01:00 AM)
h:mm tt (1:00 AM)

See more DateTime formats at Custom Date and Time Format Strings MSDN page

Modify regex to take h:mm time format in addition of hh:mm

2 Answers2