To cover the entire Political Science and International Relations (PSIR) syllabus for the UPSC exam, it is recommended to follow a well-structured timeline. This will ensure comprehensive coverage of the syllabus and allow sufficient time for revision and practice. Here is a detailed breakdown of the recommended timeline:

1. Understanding the Syllabus:
- Begin by thoroughly going through the PSIR syllabus provided by UPSC.
- Understand the different topics and subtopics included in the syllabus.
- Identify the weightage and importance of each topic based on previous year's question papers.

2. Topic-wise Allocation:
- Divide the entire syllabus into smaller topics for easier understanding and management.
- Allocate specific time for each topic based on its importance and complexity.
- Prioritize topics that carry more weightage in the exam.

3. Studying the Basic Textbooks:
- Start with the basic textbooks recommended for PSIR such as "An Introduction to Political Theory" by O.P. Gauba and "International Relations" by V.N. Khanna.
- Read these textbooks thoroughly to develop a strong foundation in the subject.
- Take notes and highlight important concepts while studying.

4. Reference Books and Study Material:
- Once the basic textbooks are covered, move on to advanced reference books such as "Indian Government and Politics" by B.L. Fadia and "International Relations" by Paul R. Viotti.
- Also, refer to additional study materials available on EduRev, a reliable online platform for UPSC preparation.

5. Current Affairs:
- Stay updated with current affairs related to political science and international relations.
- Read newspapers, magazines, and online sources to stay informed about recent developments.
- Make notes of important events and their impact on the subject.

6. Revision and Practice:
- Allocate sufficient time for regular revision of all the topics.
- Prepare concise notes and flashcards for quick revision.
- Solve previous year's question papers and take mock tests to gauge your preparation level and work on your time management skills.

7. Time Management:
- Create a study schedule and strictly adhere to it.
- Allocate specific time slots for each topic and revise accordingly.
- Prioritize difficult topics or areas where you need more practice.

8. Seeking Guidance:
- If needed, join coaching institutes or online courses for guidance and expert assistance.
- Participate in group discussions or join study groups to clarify doubts and enhance understanding.

Remember, the timeline may vary depending on an individual's prior knowledge, study pace, and available study hours. It is crucial to maintain consistency, discipline, and focus while preparing for the UPSC exam.