Most doctoral timelines fail for the same two reasons: no allowance for approvals that sit outside your control, and no allowance for revision cycles. Ethics approval commonly takes several weeks and may return with required amendments, and supervisor feedback on a full chapter rarely comes back in days.
Plan backwards from your submission deadline rather than forwards from today. Fix the submission date, then work back through viva preparation, final formatting, plagiarism check, supervisor review of the complete draft, chapter drafting, analysis, data collection, ethics approval and proposal approval. The gaps that appear are the honest picture of what you have.
Build in slack deliberately — a plan with no buffer breaks on the first delay. Review the planner at every supervision meeting and update it rather than letting it drift out of date, since a planner that no longer reflects reality stops being useful and starts being avoided.
For a typical three- to five-year Indian PhD, a realistic pattern is coursework and synopsis approval in the first year, literature review and instrument development with a pilot study early in the second, main data collection and analysis through the second and third years, and chapter writing, revision and pre-submission seminar in the final stretch. Your university's minimum and maximum duration rules and any publication requirement before submission belong on the planner as fixed constraints from the start.