Date Math

DateMath parses and applies Elasticsearch-style date math expressions in .NET. It supports expressions anchored to the current UTC time or a specific date, arithmetic with common date units, and rounding.

The package targets .NET Standard 2.0, making it compatible with modern .NET and .NET Framework 4.6.1 or later. Microsoft recommends .NET Framework 4.7.2 or later when consuming .NET Standard 2.0 libraries.

Installation

Install the package with the .NET CLI:

dotnet add package DateMath

Or with the NuGet Package Manager Console:

Install-Package DateMath

Usage

Expressions can use now as their anchor:

using DaleNewman;

DateMath.Parse("now", "yyyy-MM-dd h tt");
DateMath.Parse("now+11h", "yyyy-MM-dd h tt");
DateMath.Parse("now-13h+1y+1d-1s", "yyyy-MM-dd HH:mm:ss");
DateMath.Parse("now/d", "yyyy-MM-dd HH:mm:ss.fff");

A fixed anchor date is separated from its math expression by ||:

var result = DateMath.Parse("2016-12-31 1 PM||+11h", "yyyy-MM-dd h tt");
// 2017-01-01 12 AM

Use TryParse when you need to check whether parsing succeeded:

if (DateMath.TryParse("now+11h", out DateTime date))
{
    // Use date.
}

Use Apply when you already have a date:

var date = new DateTime(2016, 12, 31, 9, 30, 2);
var newYears = DateMath.Apply(date, "+1d/y");
// 2017-01-01 00:00:00

Operators

Unit	Meaning
y	Year
M	Month
w	Week
d	Day
h	Hour
m	Minute
s	Second

Prefix a unit with + or - to add or subtract it, such as now-10d. Prefix it with / to round down, such as now/M for the start of the current month.

Common reporting ranges include:

Range	Start	End
Last 10 days	now-10d	now
Month to date	now/M	now
Year to date	now/y	now
Sliding 60-day window	now-30d	now+30d

See the tests for more examples, the changelog for release history, and the NuGet packaging guide for local release instructions.

Contributing

Issues and pull requests are welcome in the GitHub repository. Build and test locally with:

dotnet test --configuration Release

DateMath is licensed under the Apache License 2.0.