OH2: add hours to DateTime (time zone conversation)

[Max_G]

OK, I read all the linked posts, w/o finding a solution.

I also tried the REGEX w/o luck… but think this is the way to add the +0000 to the MQTT message, which looks like this 2021-10-26T23:46:12.040463Z

This is not shown in local time, which is what I’d like to achieve.

Maybe the ‘Z’ at the end is unexpected and should be +0000 instead?

I have tried:
{mqtt="<[mymosquitto:teslamate/cars/1/since:state:REGEX(s/Z/+0000/g)]"}

But then get Regex errors, due to Regex not installed:

021-11-02 12:34:43.924 [ERROR] [core.karaf.internal.FeatureInstaller] - Failed installing 'openhab-transformation-regex': Error:
	Error downloading mvn:org.openhab.ui.bundles/org.openhab.ui.paper/[2.5.0,2.6)

So I gave up on this approach, using a rule instead.
with the help of this post:

DateTime Conversion (openHAB 2.x)

Because openHAB 3.x rules now use Java Time API instead of Jodatime, there is a new DateTime Conversion thread for openHAB 3.x. Overview In openHab 2.x there are different ways to handle Date/Time values. DateTimeType A DateTime Item carries a DateTimeType. Joda DateTime By default openHAB 2.x-Rules use a Joda DateTime class to represent time, most notably now. Epoch The lowest common denominator when working with time is to get at the epoc value. Epoc is the number of milliseconds …

I arrived at this rule:

rule "Convert UTC timestamp to local date-time"
    when
        Item TeslaM3_since changed
    then
        var Number EpochFromDateTime = (TeslaM3_since.state as DateTimeType).zonedDateTime.toInstant.toEpochMilli
        EpochFromDateTime = EpochFromDateTime + (10 * 60 * 60 * 1000)
        val DateTimeType MyDateTimeFromEpoch = new DateTimeType(new DateTime(EpochFromDateTime).toString)
        TeslaM3_since.postUpdate(MyDateTimeFromEpoch)
        logInfo(logPrefix + "1.01", "Updated time stamp")
end

However, it raised this error:

2021-11-02 14:25:00.109 [ERROR] [ntime.internal.engine.ExecuteRuleJob] - Error during the execution of rule 'Convert UTC timestamp to local date-time': No instant converter found for type: java.math.BigDecimal

I am really peeved… what an effort to add four zeros and a plus sign to a MQTT string to get the proper timestamp.

[edit1]
added log entries to rule:

rule "Convert UTC timestamp to local date-time"
    when
        Item TeslaM3_since changed or
		//         s m h D M DoW Y
		Time cron "0 0/5 * * * ?"
		// here: 10 seconds past midnight; use http://www.cronmaker.com/
    then
        var Number EpochFromDateTime = (TeslaM3_since.state as DateTimeType).zonedDateTime.toInstant.toEpochMilli
        logInfo(logPrefix + "1.01", "Updated time stamp")
        EpochFromDateTime = EpochFromDateTime + (10 * 60 * 60 * 1000)
        logInfo(logPrefix + "1.02", "Updated time stamp")
        val DateTimeType MyDateTimeFromEpoch = new DateTimeType(new DateTime(EpochFromDateTime).toString)
        logInfo(logPrefix + "1.03", "Updated time stamp")
        TeslaM3_since.postUpdate(MyDateTimeFromEpoch)
        logInfo(logPrefix + "1.04", "Updated time stamp")
end

result…

2021-11-02 14:39:43.761 [INFO ] [el.core.internal.ModelRepositoryImpl] - Refreshing model 'tesla.rules'
2021-11-02 14:39:49.982 [INFO ] [.smarthome.model.script.TeslaM3.0.01] - System Start: Tesla rules
2021-11-02 14:40:00.013 [INFO ] [.smarthome.model.script.TeslaM3.1.01] - Updated time stamp
2021-11-02 14:40:00.022 [INFO ] [.smarthome.model.script.TeslaM3.1.02] - Updated time stamp
2021-11-02 14:40:00.025 [ERROR] [ntime.internal.engine.ExecuteRuleJob] - Error during the execution of rule 'Convert UTC timestamp to local date-time': No instant converter found for type: java.math.BigDecimal