Date with now() in a specific format in a specific timezone

[#1]

In an UpdateAttribute processor I am trying to get the date of yesterday, at midnight in the CET timezone then have it transformed to a specific format in UTC.

What I did was : 
${now():minus(86400000):format('yyyy-MM-dd\'T\'00:00:00\'Z\'' , 'CET')} 
but this still gave me the time at midnight in UTC and not CET.

What I want basically is if today is 2024-06-11 I want to get : 2024-06-10T22:00:00Z

also, there is this issue with the CEST , If I specify CET is CEST not considered ? 
I just don't want to have to change my processor every 6 months a year and have something that works no matter what

[#2]

Ideally, it should return the current date minus 24 hours and convert it to a specific time zone. Please check your server time.

CET: ${now():toNumber():minus(86400000):format('yyyy-MM-dd HH:mm:ss', 'CET')}

GMT: ${now():toNumber():minus(86400000):format('yyyy-MM-dd HH:mm:ss', 'GMT')}

Midnight CET: ${now():toNumber():minus(86400000):format('yyyy-MM-dd', 'CET'):append(' 00:00:00')}

Thanks

[#3 · Accepted solution]

@ranie 

I see a couple issues with your NiFi Expression Language (NEL) statement:

1. I see some formatting issues in your java simple formatter string: 'yyyy-MM-dd\'T\'00:00:00\'Z\'.   Your single and double quotes are not balanced.
2. You are using the function "format ()" to change the timezone, but you could also use the "formatInstant()" function.  
3. You are missing the "toNumber()" function to convert the date string to a number before trying to apply a mathematically computation to it.

The Now() function will return the date current system time as the NiFi service sees it.
example: my NiFi server uses UTC timezone:

 

The toNumber() function will provide the current date and time as a number of milliseconds since midnight Jan 1st, 1970 GMT.   This number will always be a GMT value.

The formatInstant() function will allow you to take a GMT time or a Java formatted date string and reformat it for a different timezone.

Taking above feedback into consideration, the following NEL statement should work for you.

${now():toNumber():minus(86400000):formatInstant("yyyy-MM-dd'T'HH:mm:ss 'Z'", "CET")}

Pay close attention to your use of single and double quotes.

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Thank you,
Matt