diff --git a/Tools/ardupilotwaf/chibios.py b/Tools/ardupilotwaf/chibios.py
index 89e2c9df86..04d93eb872 100644
--- a/Tools/ardupilotwaf/chibios.py
+++ b/Tools/ardupilotwaf/chibios.py
@@ -496,6 +496,8 @@ def load_env_vars(env):
         env.CHIBIOS_BUILD_FLAGS += ' ENABLE_STATS=yes'
     if env.ENABLE_DFU_BOOT and env.BOOTLOADER:
         env.CHIBIOS_BUILD_FLAGS += ' USE_ASXOPT=-DCRT0_ENTRY_HOOK=TRUE'
+    if env.AP_BOARD_START_TIME:
+        env.CHIBIOS_BUILD_FLAGS += ' AP_BOARD_START_TIME=0x%x' % env.AP_BOARD_START_TIME
 
 
 def setup_optimization(env):
diff --git a/wscript b/wscript
index a97013f7fa..8c4e40d221 100644
--- a/wscript
+++ b/wscript
@@ -386,6 +386,11 @@ configuration in order to save typing.
                  default=0,
                  help='number of auxiliary IMUs')
 
+    g.add_option('--board-start-time',
+                 type='int',
+                 default=0,
+                 help='zero time on boot in microseconds')
+    
 def _collect_autoconfig_files(cfg):
     for m in sys.modules.values():
         paths = []
@@ -456,6 +461,11 @@ def configure(cfg):
     if cfg.options.num_aux_imus > 0:
         cfg.define('INS_AUX_INSTANCES', cfg.options.num_aux_imus)
 
+    if cfg.options.board_start_time != 0:
+        cfg.define('AP_BOARD_START_TIME', cfg.options.board_start_time)
+        # also in env for hrt.c
+        cfg.env.AP_BOARD_START_TIME = cfg.options.board_start_time
+
     cfg.load('ap_library')
 
     cfg.msg('Setting board to', cfg.options.board)