This simple library uses a custom PEG grammar to parse and evaluate time expressions. It allows you to write time expressions in a natural language and evaluate them to a time.Time object.

package main

import (
    "fmt"
    "time"

    "github.com/Zenithar/timexpr"
)

func main() {
    // Parse the expression
    ts, err := timexpr.Parse("tomorrow")
    if err != nil {
        panic(err)
    }

    fmt.Println(ts.Format(time.RFC3339))
}

The following expressions are supported:

• now: returns the current time
• today: returns the current date at midnight
• tomorrow: returns the current time + 1 day
• yesterday: returns the current time - 1 day
• next (NUMBER)? UNIT: returns the current time + NUMBER UNIT
• last (NUMBER)? UNIT: returns the crrent time - NUMBER UNIT
• NUMBER UNIT (ago|later|sooner) : returns the reference time - NUMBER UNIT

Where UNIT can be one of the following:

• s / sec / second / seconds for seconds
• m / min/ minute/ minutes for minutes
• h / hour / hours for hours
• d / day / days for days
• w / week/ weeks for weeks
• M / month / months for months
• y / year / years for years

To generate the parser, you need to install the pigeon tool:

go install github.com/mna/pigeon@latest

Then you can generate the parser:

cd internal/parser
pigeon -optimize-parser -optimize-basic-latin -o grammar.go grammar.peg

This project is licensed under the MIT License - see the LICENSE file for details.