better date format example

src/main.cpp

@@ -20,7 +20,7 @@ void print_usage(char *name) {
     std::cout << "  CHANNELS: number of channels to record (1 to 5)" << std::endl;
     std::cout << "  RATE: sample rate in Hz to record at (integral number)" << std::endl;
     std::cout << "  FILENAME: output file name; should include strftime() format specifiers" << std::endl;
-    std::cout << "    if CHUNKLEN is specified. For miliseconds, use %z. Example: location/recording_%Y%m%dT%H%M%S%z.wav" << std::endl;
+    std::cout << "    if CHUNKLEN is specified. For miliseconds, use %z. Example: location/recording_%Y%m%d_%H%M%S_%z.wav" << std::endl;
     std::cout << "  CHUNKLEN: length per output file in seconds; will start a new file whenever" << std::endl;
     std::cout << "    this length is reached. If not given or zero, will record a single file." << std::endl;
     std::cout << "  TOTALLEN: total recording length; will stop when this length is reached." << std::endl;