Given a cron expression, you can get the previous timestamp or the next timestamp that satisfies the cron expression.
I have used cron expression syntax to implement a new feature called deploy freeze window in Gitploy.
go get github.com/gitploy-io/cronexprImport the package, first:
import "time"
import "github.com/gitploy-io/cronexpr"prevTime := cronexpr.MustParse("0 0 29 * *").Prev(time.Now())
nextTime := cronexpr.MustParse("0 0 29 * *").Next(time.Now())You can check the detail in the _example directory.
Field name Mandatory? Allowed values Allowed special characters
---------- ---------- -------------- --------------------------
Minutes Yes 0-59 * / , -
Hours Yes 0-23 * / , -
Day of month Yes 1-31 * / , -
Month Yes 1-12 or JAN-DEC * / , -
Day of week Yes 0-6 or SUN-SAT * / , -
The asterisk indicates that the cron expression matches for all values of the field. E.g., using an asterisk in the 4th field (month) indicates every month.
Slashes describe increments of ranges. For example 3-59/15 in the minute field indicate the third minute of the hour and every 15 minutes thereafter (i.e. 3, 18, 33, and 48). The form */... is equivalent to the form "first-last/...", that is, an increment over the largest possible range of the field.
Commas are used to separate items of a list. For example, using MON,WED,FRI in the 5th field (day of week) means Mondays, Wednesdays and Fridays.
Hyphens define ranges. For example, 0-6 indicates every hours between 0 and 6 AM, inclusive.
- The return value of
NextandPrevis zero if the pattern doesn't match in five years.