Spring Boot - Jackson - datetime timezone problems - spring

Question

I am having trouble dealing with timezones across my projects.
First of all, I have two use cases:
1) A user input a DateTime with datepicker in HTML and we want to save it without timezone in the database. example input: 10.04.2018 18:00 --> we want to save exactly this date and also want to retrieve exactly this date, no matter what the timezone is on the client side. (we can think about this like a never changing date string)
2) The more common, second use case is, we enter a DateTime with datepicker in HTML and want to save the date with timezone in the database. For example:
The Clients Timezone is Europe/Istanbul and he inputs a DateTime: 10.04.2018 18:00. Now we want to save this date as Europe/Berlin in Database which would be 10.04.2017 17:00. When we retrieve the date we want to convert the date to the timezone of the client. In this example, if a client with timezone Europe/Berlin wants to retrieve the database date 10.04.2017 17:00 we would exactly retrieve: 10.04.2017 17:00. But if a client with timezone Europe/Istanbul wants to retrieve the same value 10.04.2017 17:00 we would retrieve: 10.04.2018 18:00
Now I tried to achieve this behavior by settings the webapp timezone to Europe/Berlin and parse the dates for each use case with the Moment.js library on client site. Therefore, I always expect to retrieve a Date in the timezone Europe/Berlin from my web service and then either convert to the local time zone or let the date as it is.
I am using Spring Boot with following version:
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.9.RELEASE</version>
</parent>
<properties>
<java.version>1.8</java.version>
</properties>
In my application.properties file i set those values:
spring.jpa.properties.hibernate.jdbc.time_zone=Europe/Berlin
spring.jackson.deserialization.adjust-dates-to-context-time-zone=false
spring.jackson.time-zone=Europe/Berlin
MyApplication:
#PostConstruct
void started() {
TimeZone.setDefault(TimeZone.getTimeZone("Europe/Berlin"));
}
My attributes in my model class look like this:
#Column(name = "timeFrom")
#Temporal(TemporalType.TIMESTAMP)
private Date timeFrom;
#Column(name = "timeTo")
#Temporal(TemporalType.TIMESTAMP)
private Date timeTo;
For the first use case, where I want a date which is not parsed to the local time zone i use this code to retrieve my date in javascript: (because I know that my date in database is Europe/Berlin, I convert it to this time zone in order to retrieve the exact same date as it is in the database)
var countHours = moment(timeTracking["countHours"]).tz('Europe/Berlin').format('HH:mm');
For the second use case, where i want to convert my Europe/Berlin date from the database to the local client time zone i use this code:
var timeFrom = moment(timeTracking["timeFrom"]).format('YYYY-MM-DD HH:mm');
When i pass a date from javascript via JSON and ajax to my backend i use this:
moment($("#timeRecord-timeFrom").val()).valueOf()
On serverside i receive a timestamp in milliseconds and i parse it like that:
Date dateFrom = new Date(node.get("startTime").asLong());
Now the weird part: everything I posted above is working perfectly fine on my localhost (local machine). However, as soon as I push my war file to the live system (Jelastic Spring Boot Server) I have an offset of 2 hours in my date.
The strangest part is when I commit my date via ajax and retrieve the persisted object afterward everything is fine and I have no offset. But when I do a full page reload, I immediately receive the date with 2 hours offset. However, the date is still correct in the database.
As this is only happening on the live system and not on the localhost I have no clue how to fix this.
What am I doing wrong? Would it be better to switch to JodaTime or Java8 LocalDateTime? I already tried it but ran into several build errors so stick with java.util.Date.
A best practice tutorial for my use cases would be also appreciated.