Bitcoin and other similar cryptocurrencies reduce their block reward on specific period. Such period is 4 years for Bitcoin and it is happening soon. Be up to date with date when it will happen as halving event depends on specific block and not time of event. Halving is set to happen every 210.000 blocks, but next one is planned for 630.000.
App calculates time when halving will happen depending on average speed / block time of last few hundred blocks. After halving event app will automatically start new countdown to next halving planned for some time in 2024 (block 840.000).