Chapter 3. Date and Time

With no concept of time, our lives would be a mess. Without software programs to constantly manage and record this bizarre aspect of our universe…well, we might actually be better off. But why take the risk?

Some programs manage real-world time on behalf of the people who’d otherwise have to do it themselves: calendars, schedules, and data gatherers for scientific experiments. Other programs use the human concept of time for their own purposes: they may run experiments of their own, making decisions based on microsecond variations. Objects that have nothing to do with time are sometimes given timestamps recording when they were created or last modified. Of the basic data types, a time is the only one that directly corresponds to something in the real world.

Ruby supports the date and time interfaces you might be used to from other programming languages, but on top of them are Ruby-specific idioms that make programming easier. In this chapter, we’ll show you how to use those interfaces and idioms, and how to fill in the gaps left by the language as it comes out of the box.

Ruby actually has two different time implementations. There’s a set of time libraries written in C that have been around for decades. Like most modern programming languages, Ruby provides a native interface to these C libraries. The libraries are powerful, useful, and reliable, but they also have some significant shortcomings, so Ruby compensates with a second time library written in pure ...

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