Check if a date, or interval is in the financial year
Source:R/is_date_in_fyyear.R
      is_date_in_fyyear.RdTest to check if a date, or intervals is within a given
financial year.
If given just one date it will check to see if it is in the
given financial year.
When supplied with two dates it will check to see if
any part of that date range falls in the given financial year. If the
date_end is NA it checks that date was before or during the financial
year.
See also
Other date functions:
calculate_stay(),
compute_mid_year_age(),
convert_date_to_numeric(),
convert_numeric_to_date(),
end_fy(),
end_fy_quarter(),
end_next_fy_quarter(),
fy_interval(),
last_date_month(),
midpoint_fy(),
next_fy(),
start_fy(),
start_fy_quarter(),
start_next_fy_quarter()