• clock.sleep_for() and clock.sleep_until() in rclcpp and rclpy (discussion on where sleep functions should live in rclcpp::Duration does not include a sleep() method rclcpp#1248, Added issue Add sleep function that respects ROS time rclpy#617)
• Decide if there should be a way to to enable simtime "globally" (e.g. env. var., global param server, more convenient way to pass parameter to each node)
• rclpy TimeSource activate rostime when use_sim_time parameter is set (issue Respect the use_sim_time parameter for rclpy nodes rclpy#240)
• Logging macros respecting ROS time Allow node clock to be used in THROTTLE log macros rclcpp#969 Allow node clock use in logging macros (#969) rclcpp#970
• rclpy Rate class Add Rate rclpy#443
• API on nodes in rclcpp and rclpy for creating timers with various types rclpy node.create_timer(), free function rclcpp::create_timer()
• rclpy timer constructor needs to accept a clock argument This TODO Done Timer uses ROS time by default rclpy#419

Completed

• Fixed drift in calculation of next timer time (fix calculation of next timer call rcl#291)
• tf2_ros uses ROS clock (Use ros2 time geometry2#67)
• rclpy has a Time, Duration, and Clock implementation (Time, Duration, Clock wrapping rcl rclpy#209)
• rclpy has a time source abstraction (TimeSource and support for ROS time rclpy#210)
• rclpy supports clock jump callbacks (Callbacks when time jumps rclpy#222)
• rcl timers initialized with clock (initialize timer with clock rcl#272)
• rclcpp timers initialized with clock (construct TimerBase/GenericTimer with Clock rclcpp#523)
• rclpy timers internally initialized with clock (create timer with clock rclpy#211)
• rcl clock may have multiple time jump callbacks (Clock has multiple time jump callbacks rcl#284)
• Timers in rcl trigger using ROS time (Rcl timer with ros time rcl#286)
• rclcpp time::max() and duration::max() (Add TIME_MAX and DURATION_MAX functions rclcpp#538)
• rclcpp time::seconds() (Add rclcpp::Time::seconds() rclcpp#526)
• rclcpp duration::seconds() (add Duration::seconds rclcpp#536)
• Don't activate rostime just because clock is being published in rclcpp (Don't auto-activate ROS time if clock topic is being published rclcpp#559)