[TriLUG] Why does my "every second month" cron job run on odd-numbered months?

[Brian via TriLUG]

Hi Gang,

I have a crontab entry with the following schedule spec:
0 3 1 */2 * /do/a/thing.sh

According to crontab.guru, that means “At 03:00 on day-of-month 1 in 
every 2nd month" which is what I intend.

However, also according to crontab.guru, the upcoming schedule is:

next at 2025-09-01 03:00:00
then at 2025-11-01 03:00:00
then at 2026-01-01 03:00:00
then at 2026-03-01 03:00:00
then at 2026-05-01 03:00:00

Odd-numbered months.  Why?  I would interpret "every second month" to 
mean the even-numbered months.  Is crontab.guru wrong?  Am I wrong?

Also, is there a command-line tool to answer "when will my cron tasks 
run next"?

Thanks,
-Brian