Old APC-UPS Script not working after OH3 Update - DateTime?

I just upgraded from OH2 to OH3 and got almost everything up and running again. Only an old copy-pasted rule for parsing the output of “apcaccess -u” to give me information about my APC USV is not working anymore.

Logfile says:

2021-05-17 09:30:44.263 [ERROR] [internal.handler.ScriptActionHandler] - Script execution of rule with UID 'apc-1' failed: An error occurred during the script execution: Could not invoke constructor: org.openhab.core.library.types.DateTimeType.DateTimeType(java.time.ZonedDateTime) in apc

Already back in OH2 I got the “DateTime is deprecated” warning, but it was still working.
Here ist the rule:

import java.io.BufferedReader
import java.io.StringReader
import java.util.Calendar
import java.text.SimpleDateFormat
import java.text.ParseException

rule "APC: Parse raw output from command-line tool"
	Item APC_Raw changed
	var output = APC_Raw.state.toString
	var String line
	var String[] buffer
	var String value
	var bufReader = new BufferedReader(new StringReader(output))
	var Calendar cal = Calendar.getInstance()
	var formatStrings = newArrayList('yyyy-MM-dd HH:mm:ss Z', 'yyyy-MM-dd')
	while((line = bufReader.readLine()) !== null) {
		buffer = line.split(':', 2)
		for (var i = 0; i < 2; i++) {
			buffer.set(i, buffer.get(i).trim())
    	// check if there’s an item for this key (e.g. APC_STARTTIME)
    	var item = gAPC.members.findFirst[name.equals("APC_" + buffer.get(0))]

		if (item !== null) {
			value = buffer.get(1)
			// DateTime item: try to parse date
			if (item.type == 'DateTime') {
				var succeeded = false
				for (String formatString : formatStrings) {
					try {
						if (!succeeded) { // no `break` statement in openHAB :(
							cal.setTime(new SimpleDateFormat(formatString).parse(value))
							item.postUpdate(new DateTimeType(cal).toString)
							succeeded = true
					} catch (ParseException e) { }
			// String or Number: just update the value
			} else {

    // Calculate Watts
    APC_LOAD.postUpdate(APC_LOADPCT.state as Number * 5)

How can I adapt this rule to work again?

Thanks in advance!