Exploring the Perl DateTime module
COUNTING OUT TIME
Because calendar rules are influenced by historical and political decisions, date manipulations are riddled with pitfalls. Perl’s DateTime module knows all the tricks.
If a backup script launches at 10 pm and quits at 4 am, how long did it take to run? Six hours? Well, it depends. Just think about a process that ran between March 26 and 27 in 2005 somewhere in the UK. The clocks were put forward by one hour at 1 am, and that would make five hours the right answer. If the same process had run at the same time in the USA, the answer would have been six hours, as summer time starts a week later in the US. But not in Indiana, which had not yet introduced summer time in 2005. In fact, Indiana is introducing summer time this year (2006, [2]). Fortunately, the DateTime module ([5]) from CPAN knows all these historical and future rules and provides an easy interface to even the most complex date calculations. What if you wanted to know how long the current summer time rules have been in use in the UK? Listing 1 (dsthist) discovers this by looking back from the year 2006 and checking through the month of March to find out if there is a day where you end up at 5 a.m. when adding three hours and one second to 00:59:59. If this happens, summer time was used during this year, and the script stops when it discovers that’s not the case. The display shows that 1972 was the first year with today’s summertime rules:
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
News
-
Purism Launches a Mini PC
The makers of the Librem line of Linux-based laptops have released a mini PC.
-
openSUSE Leap 15.2 Adds AI Machine Learning
With the new release of openSUSE Leap comes some exciting new features, including machine learning.
-
Google’s Nearby Sharing Could Work with Linux
Google’s answer to Apple’s AirDrop feature is rumored to work with the Linux desktop.
-
System76 Launches Ryzen-Powered Laptop
The new System76 Serval WS includes a powerful AMD Ryzen CPU.
-
Linux Mint Drops Snap
Linux Mint has officially dropped their support for Canonical’s snap packages.
-
Lenovo Upping Their Linux Support
Lenovo is now offering full certification and Linux preinstalled hardware.
-
LPI Launches FOSSlife Website
Linux Professional Institute launches FOSSlife, a website for the FOSS community.
-
Tuxedo Computers Joins the Ryzen Bandwagon
Tuxedo Computers has released the Tuxedo Boot BA15 with an AMD Ryzen 3500 CPU.
-
Linux Apps on Windows Is Coming
Linux GUI apps will be coming to Windows Subsystem for Linux.
-
Linux Usage Is on the Rise
According to NetMarketShare, Linux saw a significant bump in usage during April.