`before` should return previous timestamp

[Denys Bondarenko]

Reporting an issue

• Verify that you've looked through existing issues for duplicates before
  creating a new one
• Code sample reproducing the issue. Be sure to include all input values you
  are using such as the exact RRule string and dates.
• Expected output
• Actual output
• The version of rrule you are using
• Your operating system
• Your local timezone (run $ date from the command line
  of the machine showing the bug)

• "rrule": "^2.6.9"
• Ubuntu 20.04
• Mon 3 Apr 12:01:05 CEST 2023

Should exist ability to take previous timestamp.

const { rrulestr } = require('rrule')

const rruleStr = `DTSTART:20230227T125217Z\nRRULE:FREQ=MINUTELY;INTERVAL=10`
const r = rrulestr(rruleStr);
const nextTime = new Date('2023-02-27T12:52:17.000Z')

console.log({ nextTime }) // { nextTime: '2023-02-27T12:52:17.000Z' }

console.log('previousTime', r.before(nextTime)) // previousTime null
// expected '2023-02-27T12:42:17.000Z'
console.log('previousTime', r.before(nextTime, true)) // previousTime 2023-02-27T12:52:17.000Z

[Jecsham]

The before() method returns the previous occurrence of a recurring event based on the specified date.
In your case, r.before(nextTime) returned null because nextTime was the same as the first occurrence of the event.