Question

I am implementing a Fuzzy Date control in C# for a winforms application. The Fuzzy Date should be able to take fuzzy values like

• Last June
• 2 Hours ago
• 2 Months ago
• Last week
• Yesterday
• Last year

and the like

Are there any sample implementations of “Fuzzy” Date Time Pickers?

Any ideas to implement such a control would be appreciated

PS:
I am aware of the fuzzy date algorithm spoken about here and here, I am really looking for any ideas and inspirations for developing such a control

Answer 1

The parsing is quite easy. It can be implemented as bunch of regexps and some date calculations.

The sample below can be easily extended to suit your needs.
I’ve roughly tested it and it works at least for the following strings:

• next month, next year,
• next 4 months, next 3 days
• 3 days ago, 5 hours ago
• tomorrow, yesterday
• last year, last month,
• last tue, next fri
• last june, next may,
• jan 2008, 01 january 2009,
• june 2019, 2009/01/01

The helper class:

class FuzzyDateTime
{

    static List<string> dayList = new List<string>() { "sun", "mon", "tue", "wed", "thu", "fri", "sat" };
    static List<IDateTimePattern> parsers = new List<IDateTimePattern>()
    {
       new RegexDateTimePattern (
            @"next +([2-9]\d*) +months",
            delegate (Match m) {
                var val = int.Parse(m.Groups[1].Value); 
                return DateTime.Now.AddMonths(val);
            }
       ),
       new RegexDateTimePattern (
            @"next +month",
            delegate (Match m) { 
                return DateTime.Now.AddMonths(1);
            }
       ),           
       new RegexDateTimePattern (
            @"next +([2-9]\d*) +days",
            delegate (Match m) {
                var val = int.Parse(m.Groups[1].Value); 
                return DateTime.Now.AddDays(val);
            }
       ),

       new RegexDateTimePattern (
            @"([2-9]\d*) +months +ago",
            delegate (Match m) {
                var val = int.Parse(m.Groups[1].Value); 
                return DateTime.Now.AddMonths(-val);
            }
       ),
       new RegexDateTimePattern (
            @"([2-9]\d*) days +ago",
            delegate (Match m) {
                var val = int.Parse(m.Groups[1].Value); 
                return DateTime.Now.AddDays(-val);
            }
       ),
       new RegexDateTimePattern (
            @"([2-9]\d*) *h(ours)? +ago",
            delegate (Match m) {
                var val = int.Parse(m.Groups[1].Value); 
                return DateTime.Now.AddMonths(-val);
            }
       ),
       new RegexDateTimePattern (
            @"tomorrow",
            delegate (Match m) {
                return DateTime.Now.AddDays(1);
            }
       ),
       new RegexDateTimePattern (
            @"today",
            delegate (Match m) {
                return DateTime.Now;
            }
       ),
       new RegexDateTimePattern (
            @"yesterday",
            delegate (Match m) {
                return DateTime.Now.AddDays(-1);
            }
       ),
       new RegexDateTimePattern (
            @"(last|next) *(year|month)",
            delegate (Match m) {
                int direction = (m.Groups[1].Value == "last")? -1 :1;
                switch(m.Groups[2].Value) 
                {
                    case "year":
                        return new DateTime(DateTime.Now.Year+direction, 1,1);
                    case "month":
                        return new DateTime(DateTime.Now.Year, DateTime.Now.Month+direction, 1);
                }
                return DateTime.MinValue;
            }
       ),
       new RegexDateTimePattern (
            String.Format(@"(last|next) *({0}).*", String.Join("|", dayList.ToArray())), //handle weekdays
            delegate (Match m) {
                var val = m.Groups[2].Value;
                var direction = (m.Groups[1].Value == "last")? -1 :1;
                var dayOfWeek = dayList.IndexOf(val.Substring(0,3));
                if (dayOfWeek >= 0) {
                    var diff = direction*(dayOfWeek - (int)DateTime.Today.DayOfWeek);
                    if (diff <= 0 ) { 
                        diff = 7 + diff;
                    }
                    return DateTime.Today.AddDays(direction * diff);
                }
                return DateTime.MinValue;
            }
       ),

       new RegexDateTimePattern (
            @"(last|next) *(.+)", // to parse months using DateTime.TryParse
            delegate (Match m) {
                DateTime dt;
                int direction = (m.Groups[1].Value == "last")? -1 :1;
                var s = String.Format("{0} {1}",m.Groups[2].Value, DateTime.Now.Year + direction);
                if (DateTime.TryParse(s, out dt)) {
                    return dt;
                } else {
                    return DateTime.MinValue;
                }
            }
       ),
       new RegexDateTimePattern (
            @".*", //as final resort parse using DateTime.TryParse
            delegate (Match m) {
                DateTime dt;
                var s = m.Groups[0].Value;
                if (DateTime.TryParse(s, out dt)) {
                    return dt;
                } else {
                    return DateTime.MinValue;
                }
            }
       ),
    };

    public static DateTime Parse(string text)
    {
        text = text.Trim().ToLower();
        var dt = DateTime.Now;
        foreach (var parser in parsers)
        {
            dt = parser.Parse(text);
            if (dt != DateTime.MinValue)
                break;
        }
        return dt;
    }
}
interface IDateTimePattern
{
    DateTime Parse(string text);
}

class RegexDateTimePattern : IDateTimePattern
{
    public delegate DateTime Interpreter(Match m);
    protected Regex regEx;
    protected Interpreter inter;
    public RegexDateTimePattern(string re, Interpreter inter)
    {
        this.regEx = new Regex(re);
        this.inter = inter;
    }
    public DateTime Parse(string text)
    {
        var m = regEx.Match(text);

        if (m.Success)
        {
            return inter(m);
        }
        return DateTime.MinValue;
    }
}

Usage example:

var val = FuzzyDateTime.Parse(textBox1.Text);
if (val != DateTime.MinValue)
   label1.Text = val.ToString();
else
   label1.Text = "unknown value";