intliang created an issue (kamailio/kamailio#4214)

### Description The **<bymonth>** comparison logic in **tmrec_match()** fails to properly evaluate equivalence conditions, as shown below: ``` int check_byxxx(tmrec_t *_trp, ac_tm_t *_atp) { ... if(_trp->bymonth) { for(i = 0; i < _trp->bymonth->nr; i++) { if(_atp->t.tm_mon == (_trp->bymonth->xxx[i] * _trp->bymonth->req[i] + 12) % 12) break; } ... ```

### Troubleshooting

#### Reproduction Rule string: "20250403T100000|PT14H|weekly|20250425T000000|2|-1WE, -2WE|16|||4"

Date time: 20250416T190000

Expected output: MATCH

Actual output: NOT MATCH

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#### Debugging Data

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``` ((lldb) p _trp->bymonth->xxx[0] (int) 4 (lldb) p _trp->bymonth->req[0] (int) 1 (lldb) p _atp->t.tm_mon (int) 3 (lldb) p _trp->bymonth->nr (int) 1 ```

#### Log Messages

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#### SIP Traffic

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### Possible Solutions The **tm_mon** field in the tm struct uses a 0-11 range (January=0), while the **<bymonth>** parameter follows a 1-12 convention (January=1) as documented in the tmrec module's README. Therefore, we should first decrement the value of **_trp->bymonth->xxx[i]** by 1 for proper conversion.

### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 6.1.0-dev0 (x86_64/Darwin) 9f24f1-dirty flags: , EXTRA_DEBUGUSE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLOCKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_SEND_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, select, kqueue. id: 9f24f1 dirty compiled on 11:59:55 Apr 16 2025 with AppleClang 17.0.0.17000013 ```

* **Operating System**:

``` Darwin yintiliangdeMacBook-Pro19.local 24.2.0 Darwin Kernel Version 24.2.0: Fri Dec 6 18:41:43 PST 2024; root:xnu-11215.61.5~2/RELEASE_X86_64 x86_64 ```