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Java Forum / General / March 2008Simple date compare
I want to check if todays date <= a date retrieved from a SQL database. like this: if (today <= toDate) I only want to care about the date, and not the time. From the database I get the date with time set to all 0, but from the today = new Date() I get the time set, and if todays date = toDate the test will fail because the time partion is larger. Can anyone please help me with a simple solution? Using Calendar would be possible, but adds a lot of code. >Can anyone please help me with a simple solution? 1. use BigDate. see http://mindprod.com/products1.html#COMMON11 2. get the timestamp long, and divide by the number of milliseconds in a day to get the day number in GMT. 3. as 2, but adjust by timezone offset in millis first to get local date. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com >> Can anyone please help me with a simple solution? > > 1. use BigDate. see http://mindprod.com/products1.html#COMMON11 > > 2. get the timestamp long, and divide by the number of milliseconds in > a day to get the day number in GMT. This is not safe, it will not take in account the leap second. > 3. as 2, but adjust by timezone offset in millis first to get local > date. [quoted text clipped - 3 lines] > The Java Glossary > http://mindprod.com >>> Can anyone please help me with a simple solution? >> [quoted text clipped - 6 lines] >> 3. as 2, but adjust by timezone offset in millis first to get local >> date. The OP's only objection to the Calendar class is > Using Calendar would be possible, but adds a lot of code. In other words, laziness, even if it were true, which it isn't. Calendar lets one zero out the time fields, leaving only the date fields filled. Calendar cal = Calendar.getInstance(); cal.set( Calendar.HOUR, 0 ); cal.set( Calendar.MINUTE, 0 ); cal.set( Calendar.SECOND, 0 ); cal.set( Calendar.MILLISECOND, 0 ); It lets you directly compare one instance to another, using <http://java.sun.com/javase/6/docs/api/java/util/Calendar.html#compareTo(java.uti l.Calendar)> That's going to be a lot less code and a lot more direct than messing with milliseconds and timezone calculations. This time laziness is steering you in the direction of *more* work, not less.  SignatureLew > >>> Can anyone please help me with a simple solution? > [quoted text clipped - 30 lines] > -- > Lew Thanks for your answers. The think is that... really I'm lazy... but since I'm converting an old non Java application that uses a lot of dates without the time part, I was kind of worried that I missed the simple solution. I will just include a simple function in my utilities class that uses Calendar to return a date with time = 0. /Ulf > The think is that... really I'm lazy... "Laziness" in engineering is actually a virtue. Like other skills, the trick is knowing when to use it, and which of several alternatives is truly the lazier. > but since I'm converting an > old non Java application that uses a lot of dates without the time > part, I was kind of worried that I missed the simple solution. In this case, Calendar is the simple solution. SignatureLew >Calendar lets one zero out the time fields, leaving only the date fields filled. > [quoted text clipped - 10 lines] >milliseconds and timezone calculations. This time laziness is steering you in >the direction of *more* work, not less. But if you HAVE to think about timezones to define what you mean by "today". What you are doing is looking ahead to the day when the planet uses UTC without timezones. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com On Sun, 09 Mar 2008 10:45:09 GMT, Andrea Francia <andrea.francia@gmx.it.invalid> wrote, quoted or indirectly quoted someone who said : >> 2. get the timestamp long, and divide by the number of milliseconds in >> a day to get the day number in GMT. >This is not safe, it will not take in account the leap second. leap seconds in Java are handled by adjustments to the clock. Computationally they don't exist. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com > leap seconds in Java are handled by adjustments to the clock. > Computationally they don't exist. Could you provide a reference for this affirmation, I'm interested. Thanks On Mar 10, 2:03 am, Andrea Francia <andrea.fran...@gmx.it.invalid> wrote: > >leap secondsin Java are handled by adjustments to the clock. > > Computationally they don't exist. This is true for a POSIX-compliant system clock. Other system clocks may count leap seconds. > Could you provide a reference for this affirmation, I'm interested. > Thanks I'll offer these http://www.ucolick.org/~sla/leapsecs/timescales.html#POSIX http://www.ucolick.org/~sla/leapsecs/onlinebib.html#POSIX > I want to check if todays date <= a date retrieved from a SQL > database. [quoted text clipped - 10 lines] > > Using Calendar would be possible, but adds a lot of code. Use Calendar. I think you'll find that "a lot" is less than you fear. SignatureEric Sosman esosman@ieee-dot-org.invalid On Sun, 09 Mar 2008 09:40:08 -0400, Eric Sosman <esosman@ieee-dot-org.invalid> wrote, quoted or indirectly quoted someone who said : > Use Calendar. I think you'll find that "a lot" is >less than you fear. On the other paw, make sure you cross check you answers with manual calculation. There are a million ways to get results, but not the results you intended from Calendar. see http://mindprod.com/jgloss/calendar.html for some of the pitfalls. Also make sure your code works for different timezones or when client and server are in different timezones. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com http://geosoft.no/software/day/Day.java.html Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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