diff --git a/buildvars.sh b/buildvars.sh
index dc0a87e3fc..1dcb9c8a35 100755
--- a/buildvars.sh
+++ b/buildvars.sh
@@ -2,4 +2,4 @@
 
 # Vars exported to the build info
 echo TECTONIC_VERSION ${TECTONIC_VERSION}
-echo BUILD_TIME $(date -u '+%d_%b_%Y_%I:%M:%S%p')
+echo BUILD_TIME $(date -u '+%Y-%m-%dT%H:%M:%S%z')