Putting into words when something will happen is easier than calculating it.
This is nothing new. Since 325 CE, Christian Easter falls on "the Sunday after the ecclesiastical full moon." Easy words for hard numbers.
Even "next business day shipping " can be hard to crunch. To a human it is easy; "Tomorrow is New Years day, so if I order before then, they will send it off the day after." I just spotted something on the web that should have read like that, but reads instead: "Will be sent Friday january 2nd if you order within 364 day, 22 hour en 59 minutes! "
I am not sure what they use for makin' numbers, but not Rax. Because, expressing when in Rax, though different from just wording it, is easy. This makes Rax less prone to errors of this type.