Prepare timestamp macros.

CMake/SMDefs.cmake

@@ -18,3 +18,48 @@ else()
   set(SM_VERSION_FULL "${SM_VERSION_MAJOR}.${SM_VERSION_MINOR}-git-${SM_VERSION_GIT_HASH}")
 endif()
 
+if (CMAKE_MAJOR_VERSION STREQUAL "3")
+  # Use the CMake 3 approach whenever possible.
+  string(TIMESTAMP SM_TIMESTAMP_DATE "%Y%m%d")
+  string(TIMESTAMP SM_TIMESTAMP_TIME "%H:%M:%S" UTC)
+else()
+  if(MSVC)
+    message(STATUS "Getting date and time information via PowerShell. This may take a few seconds.")
+    execute_process(
+      COMMAND powershell get-date -format "{yyyyMMdd}"
+      OUTPUT_VARIABLE SM_TIMESTAMP_DATE
+      RESULT_VARIABLE ret
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+
+    execute_process(
+      COMMAND powershell get-date -format "{HH:mm:ss zzz}"
+      OUTPUT_VARIABLE SM_TIMESTAMP_TIME
+      RESULT_VARIABLE ret
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+  else()
+    execute_process(
+      COMMAND date "+\"%Y%m%d\""
+      OUTPUT_VARIABLE SM_TIMESTAMP_DATE
+      RESULT_VARIABLE ret
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+
+    execute_process(
+      COMMAND date "+\"%H:%M:%S %z"
+      OUTPUT_VARIABLE SM_TIMESTAMP_TIME
+      RESULT_VARIABLE ret
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+  endif()
+
+  if (NOT (ret STREQUAL "0"))
+    set(SM_TIMESTAMP_DATE "xxxxyyzz")
+  endif()
+
+  if (NOT (ret STREQUAL "0"))
+    set(SM_TIMESTAMP_TIME "xx:yy:zz ???")
+  endif()
+endif()
+