Each City officer shall submit to the City Manager an itemized estimate of the expenditures for the next fiscal year for the department or activities under the officer's control on or before the second Monday in April of each year. This estimate shall include reasons for all recommended increases and decreases as compared with appropriations for the current fiscal year. The City Manager shall prepare a complete itemized budget for the next fiscal year and shall submit it to the Council on or before the second Monday in May of each year.