ROS2 equivalent of rospy.Time.from_sec(...)

Where in ROS1 you could use rospy.Time.from_sec(...) to create a rospy.Time object representing 1 second, in ROS2 you can use rclpy.time.Time(nanoseconds=...) to achieve a similar effect.

import rclpy.time
# 5 nanoseconds after epoch
t = rclpy.time.Time(nanoseconds=5.0)

Note that the argument is given in nanoseconds, not seconds. To convert seconds to nanoseconds, multiply by 1e9:

import rclpy.time
# 5 seconds after Epoch
t = rclpy.time.Time(nanoseconds=5.0 * 1e9)

As always, epoch refers to 1970-01-01 00:00:00 UTC.