Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Chicago O'Hare Intl Airport to Kharkiv as you normally would.
Kharkiv Intl (HRK), located 5.2 mi from the city center, is the airport you fly into when you book flights from Chicago O'Hare Intl to Kharkiv. 0 airlines have flights to Kharkiv Intl from Chicago O'Hare Intl on a regular basis. Booking flights from Chicago O'Hare Intl to Kharkiv Intl should not be difficult; the airport handles an average of 0 inbound flights from Chicago O'Hare Intl per day.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Chicago O'Hare Intl Airport to Kharkiv Intl Airport flight would often be abbreviated as a ORD to HRK flight.