Issue compiling air-quality-kit for argon

having an issue compiling the (slightly modified) air-quality-kit for the argon...
when compiling, both for the cli and the vscode version of the same src, the following error is output as below...

I've looked at the includes and the chrono.h file is present...

Any suggest

Creating /Users/mike/devops/GitHub/air-quality-kit/target/5.2.0/argon/platform_user_ram.ld ...
In file included from ./inc/Particle.h:5,
from /Users/mike/devops/GitHub/air-quality-kit//src/utils.h:6,
from /Users/mike/devops/GitHub/air-quality-kit//src/utils.c:17:
./inc/application.h:33:10: fatal error: chrono: No such file or directory
33 | #include
| ^~~~~~~~
compilation terminated.
make[3]: *** [../build/target/user/platform-12-m/air-quality-kit/src/utils.o] Error 1
make[2]: *** [user] Error 2
make[1]: *** [modules/argon/user-part] Error 2
make: *** [compile-user] Error 2

  • The terminal process "/bin/bash '-c', 'make -f '/Users/mike/.particle/toolchains/buildscripts/1.13.0/Makefile' compile-user -s'" terminated with exit code: 2.
  • Press any key to close the terminal.