Date and time type for use with Protobuf

Question

I'm considering to use Protocol Buffers for data exchange between a Linux and a Windows based system.

Whats the recommended format for sending date/time (timestamp) values? The field should be small when serialized.

Answer 1

There is Timestamp message type since protobuf 3.0, that's how to create it in model:

syntax = "proto3";  import "google/protobuf/timestamp.proto";  message MyMessage {     google.protobuf.Timestamp my_field = 1; } 

timestamp.proto file contains examples of Timestamp using, including related to Linux and Windows programs.

Example 1: Compute Timestamp from POSIX time().

Timestamp timestamp; timestamp.set_seconds(time(NULL)); timestamp.set_nanos(0); 

Example 2: Compute Timestamp from POSIX gettimeofday().

struct timeval tv; gettimeofday(&tv, NULL);  Timestamp timestamp; timestamp.set_seconds(tv.tv_sec); timestamp.set_nanos(tv.tv_usec * 1000); 

Example 3: Compute Timestamp from Win32 GetSystemTimeAsFileTime().

FILETIME ft; GetSystemTimeAsFileTime(&ft); UINT64 ticks = (((UINT64)ft.dwHighDateTime) << 32) | ft.dwLowDateTime;  // A Windows tick is 100 nanoseconds. Windows epoch 1601-01-01T00:00:00Z // is 11644473600 seconds before Unix epoch 1970-01-01T00:00:00Z. Timestamp timestamp; timestamp.set_seconds((INT64) ((ticks / 10000000) - 11644473600LL)); timestamp.set_nanos((INT32) ((ticks % 10000000) * 100)); 

Answer 2

Although you aren't saying which languages you are using or what kind of precision you need, I would suggest using Unix time encoded into a int64. It is fairly easy to handle in most languages and platforms (see here for a Windows example), and Protobufs will use a varint-encoding keeping the size small without limiting the representable range too much.