bool bson_append_timestamp (bson_t *bson, const char *key, int key_length, uint32_t timestamp, uint32_t increment);
This function is not similar in functionality to bson_append_date_time(). Timestamp elements are different in that they include only second precision and an increment field.
They are primarily used for intra-MongoDB server communication.
The bson_append_timestamp() function shall append a new element of type BSON_TYPE_TIMESTAMP.
true if the operation was applied successfully, otherwise false and bson should be discarded.