Get Cst Current Date at 00:00:00 Time in Java

There are two good answers. My suggestion only differs in the detail (which is where the devil is, according to some).

First of all you should avoid using the Date class if you can. You are already using java.time, the modern Java date and time API, (LocalDateTime, LocalTime, ZoneId). You are getting all the functionality that you need from java.time. So I am assuming that you are only converting to Date because you need a Date for some legacy API that you cannot afford to upgrade to java.time just now.

    Instant startOfDay = ZonedDateTime.now(ZoneId.systemDefault())
            .truncatedTo(ChronoUnit.DAYS)
            .toInstant();
    Date oldfashionedDate = Date.from(startOfDay);
    
    System.out.println(oldfashionedDate);

.truncatedTo(ChronoUnit.DAYS) throws away the time part of the ZonedDateTime, usually leaving us with 00:00:00 on the same day in the same time zone.

Edit:

I want America Chicago time CDT

Running the above code with the default time zone of the JVM set to America/Chicago gave:

Mon Jul 12 00:00:00 CDT 2021

Getting the right Date value and getting the expected printed output are two different things since Date.toString() picks the default time zone of the JVM and uses it for rendering the string to be returned. This behaviour may give surprises. There is no way to persuade Date.toString() to use a different time zone, so the above output only comes through setting the default time zone.

Original text: There are a lot of time zones referred to as CST and there’s no way I can be sure which one you intended (and i believe that the comments stating that America/New_York is not one of them are correct). However, the only one that I could persuade the old-fashioned Date class to abbreviate CST was China Standard Time. Running the above code in Asia/Shanghai time zone gave this output:

Sat Jul 10 00:00:00 CST 2021

It looks right to me. Since you asked your question it has become Saturday 10th in China Standard Time time zone.

Any time zone will work for getting the right Date value, the start of the day in that time zone. You also wanted an abbreviation of CST in the printed output. Time zones that did not work for this include:

• Australia/Adelaide time zone. Output was Sat Jul 10 00:00:00 ACST 2021. So even though Australian Central Standard Time is sometimes abbreviated just CST, Date chose ACST.
• America/Havana. Cuba uses Cuba Daylight Time at this time of year, so CDT is output.
• America/Winnipeg and American/Chicago. North American Central Time uses daylight saving time too, so here too CDT is output.

In any case, you know which time zone you intended, so I am leaving to you to pick.

The easiest way to change the timezone is to use System.setProperty("user.timezone", "America/New_York"); in Java NOTE:: America/New_York is not CST

import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.ZoneId;
import java.util.Date;

class DateAndTimeZoneFormatter {

    public static void main(String[] args) {
        
        System.setProperty("user.timezone", "America/New_York");

        LocalDateTime date = LocalDateTime.now().with(LocalTime.MIN);
        Date dayStart = Date.from(date.atZone(ZoneId.systemDefault()).toInstant());

        System.out.println(dayStart);

    }

}

You could try to use a ZonedDateTime with a specific ZoneId:

public static void main(String[] args) {
    // define the zone to be used
    ZoneId americaChicago = ZoneId.of("America/Chicago");
    // then take the date of today
    ZonedDateTime nowInChicago = ZonedDateTime.of(
                                    LocalDate.now(),  // today
                                    LocalTime.MIN,    // start of day
                                    americaChicago    // zone
                                 );
    // define an output format
    DateTimeFormatter dtf = new DateTimeFormatterBuilder()
                                    .appendPattern("EEE MMM dd HH:mm:ss")
                                    .appendLiteral(' ')
                                    .appendZoneText(TextStyle.SHORT)
                                    .appendLiteral(' ')
                                    .appendPattern("uuuu")
                                    .toFormatter(Locale.ENGLISH);
    // then print the formatted String representation
    System.out.println(nowInChicago.format(dtf));
}

This outputs

Fri Jul 09 00:00:00 CDT 2021

Downsides:

• this won't fully match your expected output due to CST not being applied because it is daylight saving time. Therefore, CDT will be the output.
• taking a Date.from this ZonedDateTime.toInstant() will affect the values:

Applying these two lines

Date sameNowInChicago = Date.from(nowInChicago.toInstant());
System.out.println(sameNowInChicago);

will output

Fri Jul 09 07:00:00 CEST 2021

on my machine because it is configured to have a ZoneId.of("Europe/Berlin"), which will be taken into account when printing a java.util.Date.
CEST ⇒ Central European Summer Time.