I have a Date object. Now I want to add days to that Date object.
So how that can be done? Actually using Calendar object that can be done I know.
But in my case, I haven't used a calendar objects. Instead only used date object.
For Example, suppose I have a date object
Date dtStartDate=o.getStartDate();
int x=28;
Now what I want to do is to add 28 to this date object, means if the dtStartDate is 1 July 2011
then after adding 28, dtStartDate will be 29 July 2011.
Please suggest it to me.
Thanks in advance
You can add Day using below
Calendar c1 = Calendar.getInstance();
c1.add(Calendar.DAY_OF_MONTH, 1);
Here 1 is number of Day you can add.
OR
Date dtStartDate=o.getStartDate();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
Calendar c = Calendar.getInstance();
c.setTime(dtStartDate);
c.add(Calendar.DATE, 3); // number of days to add
String dt = sdf.format(c.getTime()); // dt is now the new date
Toast.makeText(this, "" + dt, 5000).show();
May be your problem solved.
You could add the equivilent number of milliseconds to the time retrieved from Date, e.g.:
long millis = dtStartDate.getTime();
millis = millis + x*24*60*60*1000;
Date dtEndDate = new Date();
dtEndDate.setTime(millis);
You can easily do this in two simple ways my friend. First one is:
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DAY_OF_MONTH, 1);
and the second one is:
Calendar cal = Calendar.getInstance();
cal.add(Calendar.HOUR_OF_DAY, 24);
I think you would like to find this thing. Though there are so many persons are there who choose the first method.
Thanks.
Related
I am trying to pass a string of the form 12:00 into milliseconds based on the current date but I seem unable to get a good understanding of how the Calendar and Date class work to achieve this.
Now I have this code:
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
Calendar startTime = Calendar.getInstance();
String alarmPref = preferences.getString(PreferenceUtility.getReminderTimes(context), "12:00");
SimpleDateFormat format = new SimpleDateFormat("HH:mm", Locale.getDefault());
Date date = format.parse(alarmPref);
startTime.setTime(date);
This unfortunaltely gives me when logged like this:
Log.d(TAG, "Time to start:" + futureTime);
Log.d(TAG, "Date: " + date);
Gives the following results:
07-25 14:45:21.057 8409-8409/com.google.developer.bugmaster D/PreferenceUtility:Time PreferenceUtility: 21:20
07-25 14:45:21.057 8409-8409/com.google.developer.bugmaster D/QuizJobScheduler: Time to start:126000
Date: Thu Jan 01 12:00:00 GMT+01:00 1970
As seen the required string is 21:20 ( as expected ) but Time to start remains at the value 126000 and hence I keep getting the date to be Date: Thu Jan 01 12:00:00 GMT+01:00 1970, which of course is a reference to the epoch date and time.
How can I get a reference date and time that refers to the time of 21:20 and for the current date the app is running. Forgive me for my ignorance as I have tried so many literature with no success most likely I am unable to understand them.
Use this code:
String time = "21:20";
String[] splittedTime = time.split(":");
Calendar calendar = Calendar.getInstance();
// Set the current date and time
calendar.setTime(new Date());
// Set the desired hour and minute
calendar.set(Calendar.HOUR_OF_DAY, Integer.parseInt(splittedTime[0]));
calendar.set(Calendar.MINUTE, Integer.parseInt(splittedTime[1]));
// Clear seconds and milliseconds
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
// the variable date will get today's date and the desired time
Date date = calendar.getTime();
I hope you understand my comments in the code
Java's Date class does not provide the means to set ONLY the time while using the current calendar day. Android's Calendar class does.
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, 21);
calendar.set(Calendar.MINUTE, 20);
This above example requires you to parse the time without a SimpleDateFormat. Splitting the string in half (using the ':') and integer parsing the two strings would give you the values to put in.
I have retrieved a Date from a SQLiteDatabase and have formatted it to how I want via the following;
String steepingDate = (c.getString(3));
SimpleDateFormat formatter = new SimpleDateFormat("dd/MMM/yyyy");
Date steepingdate = formatter.parse(steepingDate);
I now want to give the user the option to increase whatever date is in steepingdate by a certain amount of days that the user can input
I know you can use;
Date today = calendar.getTime();
calendar.add(Calendar.DAY_OF_YEAR, 10);
For example to add 10 days onto todays date
But how do you do it so that it uses steepingdate instead of todays date
Thanks
UPDATE;
The calendar is working as I want, but I now want to save the new data to the database, the full code is as following;
String steepingDate = (c.getString(3));
SimpleDateFormat formatter = new SimpleDateFormat("dd/MMM/yyyy");
Date steepingdate = formatter.parse(steepingDate);
Integer amountDays = Integer.parseInt(TSExtend.getText().toString());
Calendar ca = Calendar.getInstance();
ca.setTime(steepingdate);
ca.add(Calendar.DAY_OF_YEAR, amountDays);
DateFormat dateFormat = new SimpleDateFormat("dd/MMM/yyyy");
String newDate = dateFormat.format(ca);
I'm getting the error;
Bad class: class
java.util.GregorianCalendar
Any ideas?
To add 10 days to steepingdate, you can use:
Calendar calendar = Calendar.getInstance();
calendar.setTime(steepingdate);
calendar.add(Calendar.DAY_OF_YEAR, 10);
it the number is provided, through the user interface, you can use the View.OnClickListener and when onClick is fired, read the value from an EditText, and use this value instead of 10
Set the time of the calendar to your date, then add the days
Calendar cal = Calendar.getInstance();
cal.setTime(steepingdate);
cal.add(Calendar.DATE, 10);
UPDATE:
You can't directly format a Calendar, first get the Date from the Calendar, then format it.
String newDate = dateFormat.format(ca.getTime());
I am trying to add a list of holidays to my calendar. I am using the Caldroid library for displaying the calendar. I want to display a list of holidays in every month for which I need to select specific dates in every month. How do I do that ? The following is what I have tried:
CODE :
Calendar cal = Calendar.getInstance();
cal.add(Calendar.DATE, -18);
Date blueDate = cal.getTime();
cal = Calendar.getInstance();
cal.add(Calendar.DATE, 16);
int diff = cal.get(Calendar.JANUARY);
cal.add(diff, 10);
Date greenDate = cal.getTime();
I believed that diff would set the month to January and highlight the 11th of January cause I have given the value as 10 but it doesn't do so and I believe it is because I have instantiated the cal to getInstance() which would return the current month.
UPDATE :
Thanks to Meno, I have achieved the following but when I set the calendar to the second time, it takes only the updates value and does not set the first date (very obvious) but I want to know how to set multiple dates in a month without re-instantiating a new GregorianCalendar object for every month. Simply put, how do I set an array of dates in a month.
GregorianCalendar greg_cal = new GregorianCalendar();
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 1);
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 18);
Thanks in advance.
Your question does not appear to be clear. Nevertheless I try an answer. Instead of
cal = Calendar.getInstance(); // In Thailand this gives the buddhist calendar, do you want this?
cal.add(Calendar.DATE, 16); // 16 days from now, what is the intention or meaning???
cal.add(diff, 10); // first argument must be a defined constant in java.util.Calendar
I assume you just want to select a fixed date (as holiday). If so then you can call the set()-method and don't need to add days to move your calendar date forth and back:
GregorianCalendar cal = new GregorianCalendar(); // including currrent year
cal.set(Calendar.MONTH, Calendar.JANUARY);
cal.set(Calendar.DAY_OF_MONTH, 11);
Then you get as date the 11th of January in current year. By the way:
int diff = cal.get(Calendar.JANUARY);
This line is nonsense because:
Calendar.JANUARY is an int constant which is zero and denotes a value (the month) not a field. But the get(int)-method expects a field constant. The field constant with value zero corresponds to Calendar.ERA. Finally the line yields the era of cal, namely int diff = GregorianCalendar.AD = 1; assuming you use the gregorian calendar. This is surely not what you want???
UPDATED because of extra question in comment:
Reusing means that you don't create a new instance for the next calculation but reuse the same one (GregorianCalendar is mutable!). For example:
GregorianCalendar cal = new GregorianCalendar(); // including currrent year
cal.set(Calendar.MONTH, Calendar.JANUARY);
cal.set(Calendar.DAY_OF_MONTH, 11);
Date holiday1 = cal.getTime();
cal.set(Calendar.MONTH, Calendar.DECEMBER); // no new instance => reuse cal
cal.set(Calendar.DAY_OF_MONTH, 24);
Date holiday2 = cal.getTime();
...
I have also written about limiting to manipulations of month and day-of-month only because with manipulation of week-related fields the state of reused Calendar-instance depends on the order of field manipulations (very ugly and surprising).
Anyway, it is always safer to use immutable types which are available in Java 8 (not useable on Android), JodaTime and my alpha-state-library. I admit that the first contact with JodaTime can cause you feeling like lost because there are so many methods (the documentation standard is good for open-source but less good than for example in JSR-310). In your use-case I would use the type org.joda.time.LocalDate as start because you really have just a plain-date-use-case. Google and SO are your friends if you want to see more documentation beyond the original Joda documentation.
UPDATE due to extended question:
You have forgotten one important thing in your new code, namely to add the results of calendar setting to a holiday list, see here the modification:
List<Date> holidays = new ArrayList<Date>();
GregorianCalendar greg_cal = new GregorianCalendar();
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 1);
holidays.add(greg_cal.getTime());
greg_cal.set(Calendar.MONTH, Calendar.JANUARY);
greg_cal.set(Calendar.DAY_OF_MONTH, 18);
holidays.add(greg_cal.getTime());
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
for (Date d : holidays) {
System.out.println(sdf.format(d));
}
// output:
2014-01-01
2014-01-18
In an external library like JodaTime you would just use org.joda.time.LocalDate instead.
List<LocalDate> holidays = new ArrayList<LocalDate>();
LocalDate today = LocalDate.now();
holidays.add(today.withMonthOfYear(1).withDayOfMonth(1));
holidays.add(today.withMonthOfYear(1).withDayOfMonth(18));
It is pretty simple (similar in my unfinished date-and-time-library, too).
Does anyone here know what the best way is to calculate the date 2 days in the past?
I've got this piece of code to retrieve the current date:
public static String getDateTime (String Format){
SimpleDateFormat sdf = new SimpleDateFormat(Format);
return sdf.format(new Date());
}
But I want to be able to calculate the date 2 days in the past. So decrease the date with 2 days. Anyone who knows what the best way is to do this?
Thanks in advance
Using Calendar is probably the easiest way. Assuming that you have defined Format as per the question:
// get Now
Calendar cal = Calendar.getInstance();
// go back two days
cal.add(Calendar.DAY_OF_YEAR, -2);
// display
SimpleDateFormat sdf = new SimpleDateFormat(Format);
String string = sdf.format(cal.getTime());
Just use Calendar's add() function:
Calendar c = Calendar.getInstance();
c.setTime(yourDateObject);
c.add(Calendar.DAY_OF_MONTH, -2);
It will automatically change the month, year, etc. if necessary.
I am trying to get a calendar object set to GMT, but the getTime() always returns the time in GMT+1 (my current time). I have tried:
Calendar cal = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
Calendar cal = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
Calendar cal = new GregorianCalendar(TimeZone.getTimeZone("skeniver"));
They all apparently return GMT, because
cal.getTimeZone().getDisplayName()
returns "GMT+00:00"; but
cal.getTime().toString();
always displays the time in GMT+1.
Does anyone have any idea why this is happening?
You need to adjust for daylight savings. I'm not sure if this will help but it's code I use for adjusting any timezone to UTC in an app that's currently being used by a number of people around the world. I use Date instead of Calendar but it works...
Date dateTimeNow = new Date();
TimeZone tz = TimeZone.getDefault();
int currentOffsetFromUTC = tz.getRawOffset() + (tz.inDaylightTime(dateTimeNow) ? tz.getDSTSavings() : 0);
Date dateTimeNowUTC = new Date(dateTimeNow.getTime() - currentOffsetFromUTC);
If you want to in string then prefer the DateFormat or SimpleDateFormat for this
here is example
SimpleDateFormat sdf = new SimpleDateFormat(); // here you can also define your format of date for e.g. "dd/MM/yyyy z"
sdf.setTimeZone("GMT");
Calendar cal = Calendar.getInstance();
System.out.println(sdf.format(cal.getTime()));
Calendar.getTime() returns a Date object. In Java, a Date is just a holder to a long timestamp starting in the UNIX epoch.
To display a Date in a different TimeZone than the default, you can use a SimpleDateFormat.