Hi Arn,
We appreciate your question about the clock of the range.
During power outages, power flickers, the power cord had been disconnected and the like; the clock will have to be set.
To set the clock, please refer to page 23 of this model's user manual I have shared below.
https://downloadcenter.samsung.com/content/UM/202105/20210524105933962/NE63A6511_AA_01_EN_MES_CFR.pdf
Should you need more assistance, please feel free to get back to us via the following options:
1. Facebook Messenger: http://m.me/samsungsupport
2. Twitter: https://twitter.com/messages/compose?recipient_id=18768513
3. Samsung Community: https://us.community.samsung.com/t5/Samsung-Community/ct-p/us
When you message us, provide them this number 1144973302 and it will help our team pull up your information.
Leo