Replace src/date.cpp with C++20 <chrono> and <format>

Use workarounds for missing chrono::parse and chrono::clock_cast.

Author: jwakely

Makefile

@@ -35,13 +35,13 @@ pgms: $(PGMS)
 
 -include src/*.d
 
-bin/lists: src/date.o src/issues.o src/status.o src/sections.o src/mailing_info.o src/report_generator.o src/lists.o src/metadata.o
+bin/lists: src/issues.o src/status.o src/sections.o src/mailing_info.o src/report_generator.o src/lists.o src/metadata.o
 
 bin/section_data: src/section_data.o
 
 bin/toc_diff: src/toc_diff.o
 
-bin/list_issues: src/date.o src/issues.o src/status.o src/sections.o src/list_issues.o src/metadata.o
+bin/list_issues: src/issues.o src/status.o src/sections.o src/list_issues.o src/metadata.o
 
 bin/set_status: src/set_status.o src/status.o
 

bin/build_pgms.bat

@@ -1,7 +1,7 @@
 echo "Use -m32 switch to force 32-bit build"
-g++ %* -std=c++20 -DNDEBUG -O2 -o bin/lists.exe  src/date.cpp src/issues.cpp src/status.cpp src/sections.cpp src/mailing_info.cpp src/report_generator.cpp src/metadata.cpp src/lists.cpp
+g++ %* -std=c++20 -DNDEBUG -O2 -o bin/lists.exe  src/issues.cpp src/status.cpp src/sections.cpp src/mailing_info.cpp src/report_generator.cpp src/metadata.cpp src/lists.cpp
 g++ %* -std=c++20 -o bin/section_data.exe src/section_data.cpp
 g++ %* -std=c++20 -o bin/toc_diff.exe src/toc_diff.cpp
-g++ %* -std=c++20 -DNDEBUG -O2 -o bin/list_issues.exe src/date.cpp src/issues.cpp src/status.cpp src/sections.cpp src/metadata.cpp src/list_issues.cpp
+g++ %* -std=c++20 -DNDEBUG -O2 -o bin/list_issues.exe src/issues.cpp src/status.cpp src/sections.cpp src/metadata.cpp src/list_issues.cpp
 g++ %* -std=c++20 -DNDEBUG -O2 -o bin/set_status.exe  src/set_status.cpp src/status.cpp