Reference library
Guides
Plain-language references that explain how our calculators work and when to use them. Pick a topic below or open any guide for step-by-step examples.
Guides are written for planners, finance staff, and anyone who needs a quick answer without opening a spreadsheet. Each article links to related calculators on the site.
Business Time guides cover invoices, contracts, and working-day math. Planning guides cover notice periods, SLAs, and payroll. Reference guides explain definitions and holiday calendars.
Business Time
Net terms, invoices, working days, and calculators for operations and finance teams.
- Business Time Calculators GuideCentral guide to DateToolsHQ Business Time calculators—invoice due dates, contract end dates, SLA deadlines, business-day math, notice periods, and deadline planning in UTC.
- Net Payment Terms GuideLearn what Net 30, Net 15, and other payment terms mean, how invoice due dates are calculated, and when calendar days differ from business days.
- Invoice Due Date GuideLearn how invoice due dates are calculated from payment terms, when calendar vs business days apply, and how to handle weekend due dates with DateToolsHQ.
- Business Days Between Dates GuideLearn how to count business days between two dates, when weekends and holidays apply, and which DateToolsHQ calculators to use for deadlines and scheduling.
- Working Days GuideLearn what working days are, how they differ from business and calendar days, and which DateToolsHQ calculators to use for scheduling and deadlines.
Planning & Deadlines
Notice periods, contracts, SLAs, payroll cutoffs, and compensation planning references.
- Notice Period GuideLearn how notice periods work, how to calculate notice end dates in calendar or business days, and which DateToolsHQ calculators to use for planning.
- Employment Milestones GuideLearn how probation periods, length of service, joining dates, and retirement ages are calculated, and which DateToolsHQ calculators to use for each stage of employment.
- SLA Deadline GuideLearn how SLA response and resolution deadlines work, when to use business days or hours, and how to calculate service level agreement deadlines with DateToolsHQ.
- Contract End Date GuideLearn how contract end dates are calculated from term lengths, how notice periods interact with expiration, and which DateToolsHQ calculators to use for renewal planning.
- Compliance & Regulatory Deadlines GuideLearn how compliance obligations, audit completion deadlines, and regulatory filing due dates are calculated from a trigger or period-end date, and which DateToolsHQ calculators to use for each.
- Payroll Cutoff Dates GuideLearn what payroll cutoff dates are, how processing windows and business days affect pay schedules, and which DateToolsHQ calculators help plan submission and approval deadlines.
- How Prorated Salary WorksLearn how partial-period salary is estimated from annual pay and days worked, common hire and termination scenarios, and how to use the prorated salary calculator.
- How Overtime Pay Is CalculatedUnderstand how regular and overtime hours combine into a gross pay estimate, common multiplier rules, and how to use the overtime pay calculator.
Date Calculations
Counting days between dates, prorated amounts, and core date math concepts.
- How to Count Days Between DatesStep-by-step guidance for counting days between two dates, inclusive vs exclusive rules, and using the days between dates calculator.
- How Prorated Rent Is CalculatedLearn how partial-month rent is estimated from monthly rent and move-in or move-out dates, and how to use the prorated rent calculator.
Reference Guides
Definitions, calendars, date formats, timestamps, timezones, and how business days and working days are calculated.
- Business Days vs Calendar Days GuideLearn what calendar days and business days mean, when each applies to deadlines and contracts, and which DateToolsHQ calculators to use for invoices, SLAs, notice periods, and more.
- How Business Days Are CalculatedUnderstand how business day counts work: weekends, holidays, inclusive ranges, and how DateToolsHQ applies the rules.
- How Many Working Days Are in a Year?See how working day totals are derived from calendar days, weekends, and holidays—and how to use country and year pages for planning.
- Working Days vs Business DaysCompare working days and business days: when the terms overlap, when they differ, and which DateToolsHQ tools to use.
- How Holiday Calendars Affect Business DaysSee how public holidays change business-day counts, why calendars differ by country and employer, and how to use DateToolsHQ holiday data for planning.
- Date Calculation ReferenceA practical reference for calendar days, business days, date ranges, and which DateToolsHQ calculator fits each question.
- Date Format GuideLearn the most common date format standards—ISO 8601, US, UK, Unix timestamps, and locale-specific patterns—and how to convert between them with DateToolsHQ.
- Unix Timestamp GuideLearn what Unix timestamps are, how they work, why they are timezone-independent, and how to convert between timestamps and human-readable dates with DateToolsHQ.
- Timezone GuideLearn how timezones work, what UTC offsets and daylight saving time mean, and how to convert times between timezones using DateToolsHQ.