Решено с помощью dayComponent:
render() {
return (
<Agenda
....
dayComponent={renderDayComponent}
.....>
</Agenda>)
}
renderDayComponent = data => <CalendarDayComponent {...data} calendarData={calendarData} />;
, чтобы восстановить поведение onPress:
const CalendarDayComponent => props {
onPressed = () => {
requestAnimationFrame(() => props.onPress(props.date));
}
let items = '';
if (props.marking.marked) {
items = calendarData[date.dateString].length
}
return (
<View style={styles.container}>
<Text onPress={onPressed} style={{ color: state === 'disabled' ? 'gray' : 'black' }}>
{children}
</Text>
<Text style={styles.itemsCount}>
{items}
</Text>
</View>
)
};