Last 14 days parsed as one day

[dblock]

Coming from https://github.com/dblock/slack-strava/issues/191

bundle exec ruby -e "require 'chronic'; puts 'last 14 days: ' + Chronic.parse('last 14 days', context: :past, g
uess: false).to_s; puts 'past 14 days: ' + Chronic.parse('past 14 days', context: :past, guess: false).to_s; puts '14 days ago: ' + Chronic.parse('
14 days ago', context: :past, guess: false).to_s; puts 'last week: ' + Chronic.parse('last week', context: :past, guess: false).to_s"

last 14 days: (2025-07-12 14:00:00 -0400..2025-07-12 14:00:01 -0400)
past 14 days: (2025-06-29 12:51:15 -0400..2025-06-29 12:51:16 -0400)
14 days ago: (2025-06-29 12:51:15 -0400..2025-06-29 12:51:16 -0400)
last week: (2025-07-06 00:00:00 -0400..2025-07-13 00:00:00 -0400)

I think users expect "last 14 days" to work like "past 14 days"