A memory system includes a memory device comprising a plurality of memory blocks; and a controller suitable for controlling the memory device, wherein the controller comprises a real time clock (RTC) management circuitry suitable for generating a sudden power-off (SPO) occurrence cycle using first and second RTC values when a first SPO occurs, and then comparing the SPO occurrence cycle to a threshold value to determine whether to delay dummy page generation; and a dummy page generation circuitry suitable for generating a dummy page using one or more free pages or an incomplete program page, excluding valid pages, from a memory block, among the plurality of memory blocks, according to the determination result of the RTC manager, the incomplete program page indicating a page in which a program operation is interrupted due to an SPO.