Ubuntu Linux: trovare file tra orari specifici?

Ho trovato un SO chiamato usando Find / Grep per cercare i file tra un'ora specifica del giorno

Sulla base di questo e un Unix SE chiamato comando Grep per trovare file contenenti stringhe di testo e spostarli, ho finito con:

find . -type f -mtime -20 | grep -v -e " \(0[012345]\|18\|19\|2[0123]\)" | xargs mv -t daytime/

Ma sta spostando TUTTI i file. Fa differenza che sto usando Ubuntu?

Tutto quello che voglio fare è spostare tutti i file tra le 6:00 e le 18:00 in un'altra directory. Tutti i suggerimenti sarebbero apprezzati.

In realtà, findha già questa funzionalità:

find . -newermt "2013-01-01 00:00:00" ! -newermt "2013-01-02 00:00:00"

Dalla manpage:

-newerXY reference
       Compares  the timestamp of the current file with reference.  The
       reference argument is normally the name of a file  (and  one  of
       its  timestamps is used for the comparison) but it may also be a
       string describing an absolute time.  X and  Y  are  placeholders
       for other letters, and these letters select which time belonging
       to how reference is used for the comparison.

       a   The access time of the file reference
       B   The birth time of the file reference
       c   The inode status change time of reference
       m   The modification time of the file reference
       t   reference is interpreted directly as a time

       Some combinations are invalid; for example, it is invalid for  X
       to  be t.  Some combinations are not implemented on all systems;
       for example B is not supported on all systems.  If an invalid or
       unsupported  combination  of  XY  is  specified,  a  fatal error
       results.  Time specifications are interpreted as for  the  argu‐
       ment  to the -d option of GNU date.  If you try to use the birth
       time of a reference file, and the birth time  cannot  be  deter‐
       mined,  a  fatal  error  message results.  If you specify a test
       which refers to the birth time of  files  being  examined,  this
       test will fail for any files where the birth time is unknown.