devxlogo

Relying on the Default TimeZone

Relying on the Default TimeZone

Why Trust Us 
Calendar calendar = new GregorianCalendar();calendar.setTime(date);calendar.set(Calendar.HOUR_OF_DAY, 0);calendar.set(Calendar.MINUTE, 0);calendar.set(Calendar.SECOND, 0);Date startOfDay = calendar.getTime();

The code above calculates the start of the day (0h00). The first mistake is the missing millisecond field of the Calendar, but a major mistake is not setting the TimeZone of the Calendar object, as a result, the Calendar will use the default time zone. In a Desktop application this might be fine, but in server-side code this is a big problem. As an example, 0h00 in Tokyo is in a very different moment than in New York, so the developer should check which time zone is relevant for this computation.

Calendar calendar = new GregorianCalendar(user.getTimeZone());calendar.setTime(date);calendar.set(Calendar.HOUR_OF_DAY, 0);calendar.set(Calendar.MINUTE, 0);calendar.set(Calendar.SECOND, 0);calendar.set(Calendar.MILLISECOND, 0);Date startOfDay = calendar.getTime();
devxblackblue

About Our Editorial Process

At DevX, we’re dedicated to tech entrepreneurship. Our team closely follows industry shifts, new products, AI breakthroughs, technology trends, and funding announcements. Articles undergo thorough editing to ensure accuracy and clarity, reflecting DevX’s style and supporting entrepreneurs in the tech sphere.

See our full editorial policy.

About Our Journalist

Charlie Frank

Charlie has over a decade of experience in website administration and technology management. As the site admin, he oversees all technical aspects of running a high-traffic online platform, ensuring optimal performance, security, and user experience.
View Author
Show More