Example code for a console calendar in Ruby

calendar2.rb

# Console Calendar

DAYS_IN_MONTH = [nil, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
IS_LEAP_YEAR = Time.now.year % 400 == 0 || (
  Time.now.year % 4 == 0 && Time.now.year % 100 != 0
)
HIGHLIGHT_CURRENT_DAY = true

def days_in_month(month)
   return 29 if Time.now.month == 2
   DAYS_IN_MONTH[month]
end

year = Time.now.year
month = Time.now.month
time = Time.new year, month
space = time.wday * 3 # pading for weekday start
days_in_month = days_in_month(month)
puts time.strftime("%B %Y").center 22
puts " Su Mo Tu We Th Fr Sa"
print " " * space
1.upto(days_in_month) do |day|
  #print "#{day}".rjust 3, " "
  if Time.now.day == day && HIGHLIGHT_CURRENT_DAY
    print " ✅️"
  else
    print "#{day}".rjust 3, " "
  end
  space += 3
  puts if [ 21, 42, 63, 84 ].include? space
end; puts

HIGHLIGHT_CURRENNT_DAY

There's a typo, should be:

HIGHLIGHT_CURRENT_DAY

HIGHLIGHT_CURRENNT_DAY

There's a typo, should be:

HIGHLIGHT_CURRENT_DAY

fixed