How to convert java date to Pega Date and DateTime

In Pega, date would be stored as YYYYMMDD.
In Java, we have many acceptable formats. Let's say 2018-09-29 YYYY-MM-DD

If we have to convert Java date to Pega Date, you can use ConvertDate function.

Java Date to Pega Date:
@ConvertDate(Param.JavaFormatDate)
where Param.JavaFormatDate=2018-09-29

Pega Date to Pega Date time:
There are many ways to achieve it. Easiest way is by using function @addToDate(Param.PegaDate,0,0,0,0,0)
by keeping no of days, hours, mins, sec, ms to 0.
For example, if Param.PegaDate=20180929 then output after conversion to datetime is : 20180929T000000.000 GMT
Note: This would give a datetime in format of GMT

This is the basic understanding. If we are clear with this, we can easily achieve requirements.

Scenario with timezone:
When Pega datetime of format GMT is saved to DB, let's say if the server is in HKT
In the above example, on clipboard
Pega datetime=20180929T000000.000 GMT
In DB datetime =2018-09-29 08:00:00.000
Note: HKT=GMT+8hours