Signal every 7 day

There are some way to obtain a signal every 7 or n day? ... timer not help for this.

You just need to increase the period measured.

What is it for? A maintainence reminder or similar?

Doubt if most people would have it as a HAL component, if there was a break for any reason it would reset to zero.

You could program one to start with linuxcnc and stop when it unloaded, writing to file or similar.
Depends what you want to do with it

What is it for? A maintainence reminder or similar?

Do you want to set a HAL pin every 7 days

yess maintenance reminder ..... cron job sound no good......... my god .... I can use custom Mxxx with bash routine that read my timedayfile.txt, if date time is 1 day bigger add in mycounterfile.txt +1 and refreh timedayfile.txt value with today date..... if in mycounterfile.txt I find a number with 7 value setp myhalpin -> mycustomMessage.trigger.... is right?

Writing to file sounds more promising.

Unless the machine is running 24\7, presumably you want a cumulative total and it might not be switched on, or realtime available when the cron job is scheduled

thaks at all ...... but normally I work to reduce the cronjob with linuxcnc...... I am no expert but I doubt that the cronjob disturb the work of LinuxCNC .... am I wrong ?

in any case write to files it give the results more reliable and manageable ....