An apparatus (200; 500) for managing message transmission delay, the apparatus configured to be included in a client device, the apparatus comprising: a time gap calculator configured to: transmit a request message for requesting local time information of a message server to the message server, receive, from the message server, a response message including the local time information of the message server, wherein the local time information included in the response message comprises a transmission time (Time 2) of the response message based on local time of the message server, calculate a round trip time, RTT, using a transmission time (Time 1) of the request message based on local time of the client device and a reception time (Time 3) of the response message based on the local time of the client device, and calculate a time gap between the local time of the message server and the local time of a client device, wherein the time gap is calculated as a mathematical difference between: a difference between the transmission time (Time 2) of the response message and the transmission time (Time 1) of the request message, and one half of the round trip time, RTT; and a delay time calculator configured to: calculate, when the client device receives a push message including a transmission time (Time 4) based on the local time of the message server from the message server, a delay time for the push message, wherein the delay time is calculated as a mathematical sum of: a difference between the transmission time (Time 4) included in the push message and a reception time (Time 5) of the push message based on the local time of the client device, and the time gap. a time gap calculator configured to: transmit a request message for requesting local time information of a message server to the message server, receive, from the message server, a response message including the local time information of the message server, wherein the local time information included in the response message comprises a transmission time (Time 2) of the response message based on local time of the message server, calculate a round trip time, RTT, using a transmission time (Time 1) of the request message based on local time of the client device and a reception time (Time 3) of the response message based on the local time of the client device, and calculate a time gap between the local time of the message server and the local time of a client device, wherein the time gap is calculated as a mathematical difference between: a difference between the transmission time (Time 2) of the response message and the transmission time (Time 1) of the request message, and one half of the round trip time, RTT; and transmit a request message for requesting local time information of a message server to the message server, receive, from the message server, a response message including the local time information of the message server, wherein the local time information included in the response message comprises a transmission time (Time 2) of the response message based on local time of the message server, calculate a round trip time, RTT, using a transmission time (Time 1) of the request message based on local time of the client device and a reception time (Time 3) of the response message based on the local time of the client device, and calculate a time gap between the local time of the message server and the local time of a client device, wherein the time gap is calculated as a mathematical difference between: a difference between the transmission time (Time 2) of the response message and the transmission time (Time 1) of the request message, and one half of the round trip time, RTT; and a difference between the transmission time (Time 2) of the response message and the transmission time (Time 1) of the request message, and one half of the round trip time, RTT; and a delay time calculator configured to: calculate, when the client device receives a push message including a transmission time (Time 4) based on the local time of the message server from the message server, a delay time for the push message, wherein the delay time is calculated as a mathematical sum of: a difference between the transmission time (Time 4) included in the push message and a reception time (Time 5) of the push message based on the local time of the client device, and the time gap. a difference between the transmission time (Time 4) included in the push message and a reception time (Time 5) of the push message based on the local time of the client device, and the time gap.