https://www.postgresql.org/docs/current/datatype-datetime.html

공식 문서에 다음과 같이 쓰여있습니다.

단어 뜻 그대로 과거로 영원, 미래로 영원을 뜻합니다.

숫자에서 무한 개념의 단어입니다.

8.5.1.4. Special Values

PostgreSQL supports several special date/time input values for convenience, as shown in Table 8.13. The values infinity and -infinity are specially represented inside the system and will be displayed unchanged; but the others are simply notational shorthands that will be converted to ordinary date/time values when read. (In particular, now and related strings are converted to a specific time value as soon as they are read.) All of these values need to be enclosed in single quotes when used as constants in SQL commands.