The simplest approach would be to convert the Year string to an integer value and then compare it with 2020.
If the field to be tested contained a date string you could strip out the year character from the rest of the date [e.g. using the left() function] before converting it to an integer. You could alternatively convert the date string to a date type and then use the dateSubtract() function to compare it with a threshold date of 2020-01-01. Using the date functions is more processsor intensive than using numeric comparisons so the first option is probably the fastest method. However, you may will need to use the dateSubtract() function to compare two arbitrary date values.
Note, you will need to handle Null values in your code unless the value to be tested can never be Null.