The U.S. Government Accountability Office's Schedule Assessment Guide, GAO-16-89G, published 22 December 2015, tells auditors and program managers to confirm that the critical path is valid. In the guide's words, that path is the longest-duration sequence of activities. It sets the earliest date the program can finish. If something on that path slips, the finish slips, unless you change the logic or the durations on purpose. Activities off the path can slip only as far as their float allows. Float, also called slack, is the time a predecessor can move before the program's estimated finish moves. The guide's rule of thumb: activities on the critical path have the least float. A huge amount of float is not comfort. It is often a sign that logic is missing.
You do not need scheduling software to use the idea on a deadline you share with other humans. You need to know which of their dates, if missed, moves yours, and which are merely nearby.
A predecessor is a fact, not a personality
Map the chain on paper before you negotiate tone. Write your external finish at the right. To its left, write the last thing you must receive in order to start your last piece of work. To the left of that, write who produces it and the date they have actually named, not the date you hope they meant. Keep walking left until you hit something that has already happened. The longest chain, the one with the least spare time between those dates, is your critical path for this delivery. Everything else can be late without moving your finish, up to the float those items have.
GAO warns that nonworking days are not float. A weekend is not slack you cleverly saved. It is a calendar. If someone's "Friday" output arrives Monday because they do not work Saturday, your chain already included that, or it was wrong. The guide also says float should not be treated as a reserve of spare time you can spend on extra wishes. Float is shared by the activities on a path. If you spend it on a side request, the next person on the path inherits a tighter date and nobody agreed to that.
Ask each predecessor one question that sounds blunt because it is: "If you miss the date you gave me, which of my dates moves?" If they cannot answer, they have not seen your chain. Show it to them. A date offered without knowledge of the successor is a wish. The GAO language for a schedule that hides logic is not polite. Invalid logic makes the earliest finish unknowable. You are allowed to say you cannot promise Friday if their input has no date.
The date behind the date
People announce deadlines that are buffers, political markers, or someone else's panic. Your job is to find the date that is tied to a real successor, the one that moves a finish if it slips. Try three questions, in order, and stop when you get a concrete answer.
- What happens the day after this date if the thing is not ready? If the answer is "we remind you," you are not on a critical path. You are on a nagging path. Nagging paths still matter, but they are not the same emergency.
- Who is the next person waiting, and what do they do with it the day it arrives? A named person and a named action means the date is carrying work. "Leadership wants an update" is not yet a named action.
- Is there float, and who is allowed to use it? If they have three days of spare time and you have none, the honest schedule gives the spare time to the path that has zero, which is what GAO says resource moves are for: from activities that can slip toward activities that cannot. If they have no float either, both of you need a scope or date decision, not a pep talk.
Write down the answer. Memory will upgrade their "hopefully Thursday" into "they promised Thursday" by Friday morning. The written line is the predecessor. The hopeful sentence is not on the path.
Hand the work across in a form they can start
A predecessor that arrives as a pile is a late predecessor that looks on time. Define the handoff as an object: the file, the decision, the list of open questions, the format. GAO's scheduling logic cares whether the successor can start, not whether the predecessor feels finished. If you are the predecessor for someone else, give them the same courtesy. Your internal "almost" is not their start. If you are waiting, say what "startable" means before the date, not in the complaint after it.
Here is an illustrative example, made up to show the chain and not based on a client. You owe a board memo on the 30th. The memo needs figures from Priya's team. Priya's team needs a locked product list from a vendor. The vendor said "mid-month." Mid-month is not a date, so the chain has a hole. You ask Priya what day the list must arrive for her figures to reach you on the 22nd, which is the last day you can still draft. She says the 15th. You ask the vendor for the 15th in writing and for what slips if they deliver on the 18th. If the 18th pushes Priya past the 22nd, your 30th moves, and the board should hear that on the 12th, while there is still a choice. Waiting until the 28th to discover "mid-month" meant the 18th is how shared deadlines become personal failures.
The names in that paragraph are labels in an illustration. Do not go looking for them.
When you cannot move their date
Sometimes the predecessor date is real and immovable: a filing deadline, a ship date, a hearing. Then your float has to come from your own scope. Cut the part of your work that is not on the path. Do not cut the part that is. Teams do the opposite under stress because the off-path work is often more visible and more fun. GAO's attention rule is the corrective: management attention belongs on the activities that determine the earliest finish. The side quest can wait in proportion to its float.
If several outside dates feed one integration step, the integration cannot start at the earliest of those dates. It starts at the latest. That latest date is the one to manage. The others are float unless they slip past it. This is the same logic as a critical path through a merge. You do not get credit for the three inputs that were early.
For the reserved time that should sit in front of that merge, see why buffer days are not leftover laziness. For the case where the path grew because someone added work, see scope creep. Other people's deadlines are specifically about sequence. Sequence errors feel like rudeness. They are usually missing logic.
What GAO is not saying about your Tuesday
GAO-16-89G is a guide for assessing capital-program schedules, written for auditors and agencies, with ten best practices and a stack of case studies from federal programs. It is not a law governing your group chat, and it does not promise that a correct critical path makes a program cheap or popular. The press note that accompanied the guide says a reliable schedule helps show whether dates are realistic. It does not say every realistic date will be met. Risks still happen. The guide's answer to risk is a schedule risk analysis and a contingency, which is a different article. This one only asks you to stop treating every nearby date as if it could move your finish.
Which date on your list, if it slipped by two days, would actually move the thing you owe?
The schedule guide
- U.S. Government Accountability Office. (2015, December 22). Schedule Assessment Guide: Best Practices for Project Schedules (GAO-16-89G). Best practices on the critical path and on total float. gao.gov/products/gao-16-89g · PDF