diff --git a/cad/opencascade/files/patch-src_DataExchange_TKDESTEP_STEPConstruct_STEPConstruct__AP203Context.cxx b/cad/opencascade/files/patch-src_DataExchange_TKDESTEP_STEPConstruct_STEPConstruct__AP203Context.cxx
new file mode 100644
index 000000000000..e448f20b8ba1
--- /dev/null
+++ b/cad/opencascade/files/patch-src_DataExchange_TKDESTEP_STEPConstruct_STEPConstruct__AP203Context.cxx
@@ -0,0 +1,58 @@
+commit 8a3f204601ddb1cc6063236f53f07e8bf19d9e63
+Author: Christoph Moench-Tegeder <cmt@burggraben.net>
+Date:   Mon Jun 15 20:51:37 2026 +0200
+
+    Data Exchange - on FreeBSD, check for standard-conforming timezone variable (#1277)
+    
+    On FreeBSD, "timezone" from time.h only recently started following the
+    POSIX/XSI standard. Before that switch, timezone used to be the
+    historical BSD function "char *timezone(int, int)", which is
+    obviously not what the code here expects.
+    
+    For older FreeBSDs, provide a workaround using time() and localtime().
+    
+    The closest __FreeBSD_version increment I could find is 1500019,
+    compare
+    https://cgit.freebsd.org/src/commit/include/time.h?id=a34940a9756ac8edce36fec176949ee82e9235b4
+    and
+    https://docs.freebsd.org/en/books/porters-handbook/versions/#versions-15
+    
+    See https://pubs.opengroup.org/onlinepubs/9799919799/ for official
+    POSIX documentation, especially
+    - https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/time.h.html
+      for time.h
+    - https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap02.html#tag_02_01_04
+      for X/Open System Interfaces (XSI)
+    and also FreeBSD man pages (especially the difference between versions)
+    - https://man.freebsd.org/cgi/man.cgi?query=tzset&apropos=0&sektion=0&manpath=FreeBSD+14.4-STABLE&format=html
+    - https://man.freebsd.org/cgi/man.cgi?query=tzset&apropos=0&sektion=0&manpath=FreeBSD+15.0-STABLE&format=html
+    
+    CLA: 1143
+
+diff --git src/DataExchange/TKDESTEP/STEPConstruct/STEPConstruct_AP203Context.cxx src/DataExchange/TKDESTEP/STEPConstruct/STEPConstruct_AP203Context.cxx
+index e63c9c9710..ad7ce1c097 100644
+--- src/DataExchange/TKDESTEP/STEPConstruct/STEPConstruct_AP203Context.cxx
++++ src/DataExchange/TKDESTEP/STEPConstruct/STEPConstruct_AP203Context.cxx
+@@ -64,6 +64,11 @@
+   #include <pwd.h>
+ #endif
+ 
++// needed for timezone XSI compatibility check
++#if defined(__FreeBSD__)
++  #include <sys/param.h>
++#endif
++
+ //=================================================================================================
+ 
+ STEPConstruct_AP203Context::STEPConstruct_AP203Context()
+@@ -112,6 +117,10 @@ occ::handle<StepBasic_DateAndTime> STEPConstruct_AP203Context::DefaultDateAndTim
+ #if defined(_MSC_VER) && _MSC_VER >= 1600
+     long shift = 0;
+     _get_timezone(&shift);
++#elif defined(__FreeBSD__) && __FreeBSD_version < 1500019
++    time_t     time_clock  = time(NULL);
++    struct tm* time_struct = localtime(&time_clock);
++    int        shift       = int(time_struct->tm_gmtoff);
+ #else
+     int shift = int(timezone);
+ #endif