How to set datetime to end of day in java

Question

I want to set datetime of day as: startDate=2018/03/28 00:00:00 and endDate=2018/03/28 23:59:59

    Calendar cal = Calendar.getInstance();
    SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd 00:00:00");
    SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd 23:59:59");
    String str1=sdf1.format(cal.getTime());
    String str2=sdf2.format(cal.getTime());
    Date startDate = sdf1.parse(str1);
    Date endDate = sdf2.parse(str2);

My problem:program is working and output endDate=2018/03/28 00:00:00

Would you please point out any mistakes to me in code?

update: i used debug and it's working correct with

String str2=sdf2.format(cal.getTime());//2018-03-28 23:59:59

but when change string==>date is not correct with output 2018/03/28 00:00:00

Answer 1

If you want to initialize Date instances from a formatted string with both date and time then time codes should be added to the SimpleDateFormat pattern to parse strings in that format.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date startDate = sdf.parse("2018-03-28 00:00:00");
Date endDate   = sdf.parse("2018-03-28 23:59:59");

If you want to simply set the hour, minute, and second on the current date then use a Calendar instance and set fields on it accordingly.

 Calendar cal = Calendar.getInstance();
 cal.set(Calendar.HOUR_OF_DAY, 0);
 cal.set(Calendar.MINUTE, 0);
 cal.set(Calendar.SECOND, 0);
 cal.set(Calendar.MILLISECOND, 0)

 Date startDate = cal.getTime();
 cal.set(Calendar.HOUR_OF_DAY, 23);
 cal.set(Calendar.MINUTE, 59);
 cal.set(Calendar.SECOND, 59);
 cal.set(Calendar.MILLISECOND, 999)
 Date endDate = cal.getTime();

And next output the Date in a particular format:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
System.out.println(sdf.format(startDate));
System.out.println(sdf.format(endDate));

Output:

2018/03/28 00:00:00
2018/03/28 23:59:59

Dealing with time zones

If time zone is other than the local time zone then it's a good idea to be explicit with what timezone you're working with. Calendar and SimpleDateFormat instances must be consistent with what timezone you're dealing with or the date and/or times may be off.

TimeZone utc = TimeZone.getTimeZone("UTC");
Calendar cal = Calendar.getInstance(utc);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
sdf.setTimeZone(utc);