-Wdate-time unknown to gcc
gcc-4.8 which is the default even in openSUSE 42.3, does not understand the newly added -Wdate-time warning and chokes on that.
commit 208bb92c9f75fee9014929148f726a490e6268e7
Author: Karel Slany <karel.slany@nic.cz>
Date: Wed Jun 14 11:24:32 2017 +0200
Added -Werror=format-security compiler flag.
diff --git a/datovka.pro b/datovka.pro
index 024a56861e5a..e6ce511ba5b2 100644
--- a/datovka.pro
+++ b/datovka.pro
@@ -141,6 +141,7 @@ unix:!macx {
QMAKE_CXXFLAGS = \
-g -O0 -std=c++11 \
-Wall -Wextra -pedantic \
+ -Wdate-time -Wformat -Werror=format-security \
-Isrc/views
INCLUDEPATH += \