Internal Clock variables

I am working on a domotica system for an off grid, off internet house. It involves some measurements like temperature, humidity battery voltage etc..
To make sense the stored values should be timestamped, so I added a DCF77 RTC receiver that works fine.
The DCF77 signal is neatly converted in time, date, hour etc.. variables for further use.
Sometimes the receiver fails, which makes that we have to wait another minute to get a reading.
In the mean time, my Arduino's Mega, Ethernet, Uno keep track of the current time just like I they have an internal clock on board.
The sketch I found include a library "DCF77.h" and "TimeLib.h", stuff dating from 2012 or so.
Making a little mistake, the TimeLib.h library was unwillingly commented out
To my surprise my sketch keeps running perfectly, notwithstanding that TimeLib.h defines the relevant variables like month, second, hour etc..
An example in the DCF77-master library called "InternalClockSync.ino" demonstrates this.
Question : Has the contents of TimeLib.h been included in the evolving Arduino IDE in the mean time, making TimeLib.h (and probably many others) obsolete?

Are you sure it wasn’t also included in some other header file that you did include?

Line #9 of the DCF77.h file

#include <TimeLib.h>