I added breakpoints to your code to debug and found the cause of the problem:

1. validateFieldsAndScroll you can pass {force: true} as the second parameter see the document )), otherwise, the unmodified fields will not trigger the check again.
2. the value you get in onChange is the new value, but this value has not been updated to the state of the component, that is, the value you get by calling form.getFieldValue ('timeStart') is still the old value;

for the above reasons, the solution is also relatively clear:

1. add {force: true} parameters to validateFieldsAndScroll ;
2. put the call to form.validateFieldsAndScroll in setTimeout (() = > {}, 0) inside

has no one ever encountered such a need?

it is fine to add custom checks to both date boxes. One example and the other one is fine by its own judgment logic

{
    getFieldDecorator('date1', { initialValue: moment(),
        rules: [{
            required: true,
            validator: (rule, value, callback) => {
            const edate = getFieldValue('date2');
            if (moment(edate).isBefore(moment(value))) {
                callback();
            } else {
                callback('you error message');
            }
        },
        message:'xxx'
    }]
})
    (
        <DatePicker
            placeholder='1'
            format='YYYY-MM-DD dddd'
            onChange={date => { /*do something*/ }}
        />
)}