How to Extract datetime value with AM/PM && remember its position from string

Question

I've see this post. What if my string is string x = "Tomorrow 04-26-19 09:14AM sunrise.";, basically the datetime value is always in mm-dd-yy hh:mm<AM/PM> format. So I'd need to extract this value of 04-26-19 09:14AM and remember the starting position which = 9.

Does it always occur after the first space and end before the last one. Otherwise, use a simple Regex to pick out the match, and then do a second pass using `string.IndexOf` (unless you need to do a million of these operations) — Flydog57, Jul 22 '20 at 01:31
@Flydog57 - Even with a million operations your suggestion sounds quite fast. — Enigmativity, Jul 22 '20 at 01:46
@Flydog57 - Regex matches keep index anyway. So actually quite fast. — Enigmativity, Jul 22 '20 at 01:49

score 1 · Accepted Answer · answered Jul 22 '20 at 04:30

This works nicely for me:

string x = "Tomorrow 04-26-19 09:14AM sunrise.";

var regex = new Regex(@"\d{2}-\d{2}-\d{2} \d{2}:\d{2}(AM|PM)");

var match = regex.Match(x);

if (match.Success)
{
    var prefix = x.Substring(0, match.Index);
    var value = DateTime.ParseExact(match.Value, "MM-dd-yy hh:mmtt", System.Globalization.CultureInfo.CurrentCulture);
    var suffix = x.Substring(match.Index + match.Length);
}

It's using Regex to find a potential DateTime string and then determines the prefix part of the string, the DateTime value, and the suffix part of the string.

It gives me:

"Tomorrow "
2019/04/26 09:14:00
" sunrise."

score -1 · Answer 2 · answered Jul 22 '20 at 02:07

If "tomorrow" and "sunshine" aren't necessarily always going to be present in a string like x but the format of this string will be similar, I'd probably split these strings according to the space character like this.

x.Split(' ')

with indices

string strDate = x.Split(' ')[1];
string strTime = x.Split(' ')[2];

& then join those sets of strings

string dt = $"{strDate} {strTime}";

& then probably use the DateTime.ParseExact functionality to craft an actual DateTime object out of what I parsed.

DateTime.ParseExact(dt, "MM-dd-yy hh:mmtt", System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.AssumeLocal)

I generally use assumelocal so that I know the time won't be UTC. "tt" is a placeholder for AM or PM.

If this is something you'll have to do iteratively, then I would probably create a method for this, and then simply call it routinely.

How to Extract datetime value with AM/PM && remember its position from string

2 Answers2