Using Howard Hinnant's free, open-source header-only and thread-safe datetime library.

https://howardhinnant.github.io/date/date.html
All logs will display a datetime in format "2021-02-23 12:57:21.1023272" UTC, instead of simply displaying double formatted timestamp.

Update ccpp-linux.yml

Soon github actions will use ubuntu 20.04 as latest. Let's avoid surprised and stick to ubuntu-18.04 fow now.

.github/workflows/ccpp-linux.yml

@@ -5,13 +5,12 @@ on: [push]
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
 
     steps:
     - name: Check out repository
       uses: actions/checkout@v2
-      with:
+      with:      
-        depth: 1
         submodules: 'recursive'
     - name: Run Cppcheck
       uses: Bedzior/run-cppcheck@master

tdutils/CMakeLists.txt

@@ -251,6 +251,7 @@ set(TDUTILS_SOURCE
   td/utils/ThreadLocalStorage.h
   td/utils/ThreadSafeCounter.h
   td/utils/Time.h
+  td/utils/date.h
   td/utils/TimedStat.h
   td/utils/Timer.h
   td/utils/TsFileLog.h

tdutils/td/utils/logging.cpp

@@ -23,6 +23,7 @@
 #include "td/utils/port/thread_local.h"
 #include "td/utils/Slice.h"
 #include "td/utils/Time.h"
+#include "td/utils/date.h"
 
 #include <atomic>
 #include <cstdlib>
@@ -65,6 +66,8 @@ Logger::Logger(LogInterface &log, const LogOptions &options, int log_level, Slic
     return;
   }
 
+  using namespace date;
+
   // log level
   sb_ << '[';
   if (log_level < 10) {
@@ -81,7 +84,8 @@ Logger::Logger(LogInterface &log, const LogOptions &options, int log_level, Slic
   sb_ << thread_id << ']';
 
   // timestamp
-  sb_ << '[' << StringBuilder::FixedDouble(Clocks::system(), 9) << ']';
+  //sb_ << '[' << StringBuilder::FixedDouble(Clocks::system(), 9) << ']';
+  sb_ << '[' << date::format("%F %T", std::chrono::system_clock::now()) << ']';
 
   // file : line
   if (!file_name.empty()) {