获取或是设置时刻:

now_t = rospy.Time.now()  # 获取当前时刻
t= rospy.Time(1234)  # 自定义时刻: 1234s 或者使用 t= rospy.Time.from_sec(1234)

rospy.loginfo("时刻:%.2f, %.2f",t.to_sec(),now_t.to_sec())

持续时间:

du = rospy.Duration(5)  # 设置一个时间区间(间隔)

rospy.sleep(du) #休眠函数

before_now = now_t - du  # 时间运算
after_now  = now_t + du 
# now = now + now  # 非法

定时器操作:

"""    
def __init__(self, period, callback, oneshot=False, reset=False):
    @param period: 回调函数的时间间隔
    @type  period: rospy.Duration
    
    @param callback: 回调函数
    @type  callback: function taking rospy.TimerEvent
    
    @param oneshot: 设置为True，就只执行一次，否则循环执行
    @type  oneshot: bool
    
    @param reset: if True, timer is reset when rostime moved backward. [default: False]
    @type  reset: bool
"""
def doMsg(event):  # event: rospy.TimerEvent
    rospy.loginfo("+++++++++++")
    rospy.loginfo("当前时刻:%s",str(event.current_real))

rospy.Timer(rospy.Duration(1),doMsg)
rospy.spin()  # 有回调函数别忘记这个 ~

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参考资料如下： ROS理论与实践